Explain xkcd: It's 'cause you're dumb.
Randall provides us with a – presumably anecdotal – montage of the Internet's changing attitude towards different instant messaging protocols, framed within the context of a team trying to remain in communication while tolerating each others' different tastes.
Although one-on-one "talk" programs date back to 1960s mainframes, Internet Relay Chat (IRC) was one of the first real-time group communication protocols, invented in 1988. While it remains the format on which most later apps were based, the convenience and accessibility of other protocols such as AIM and Skype gradually exceeded IRC in popularity. Many users took to the new environments, but others preferred the old and familiar, hence schisms between groups began to grow.
Skype and Slack are both proprietary centralized communication protocols (usually used through their official clients). Skype focuses mainly on voice communication, be it for personal or business use, and own installable client, while Slack relies almost entirely on text communication, focuses on work communication and works completely well in its own web client, even though official desktop and mobile clients are available as well. Slack also features a huge customizability (bots, plugins) possibly inspired by IRC, and its users need to create communication teams, working inside subdomains at *.slack.com. It is possible to connect to Slack via IRC as well, using a gateway feature, if allowed by the team's admin.
Randall here seems to be commenting on the persistence of IRC; while generally considered to be ancient software in comparison to newer and still-competing protocols, its endless customizability has led some people to support it above all others.
Extrapolating for the sake of humor, the joke here lies in a particularly uncommon but memorable type of Internet denizen: even in a far-off distant future where the world's technology has led to a superlative messaging network encompassing all people in some supposed, incredible bliss, there is always - in Randall's vision - going to be That IRC Guy. This might also be a reference to the scenarios in science fiction stories such as Isaac Asimov's concept of Galaxia in the Foundation novels, or the concept of a merged human-computer intelligence as in The Last Question. , the concept of which is most notably highlighted by this line:
[...] One by one Man fused with AC, each physical body losing its mental identity in a manner that was somehow not a loss but a gain. [...]
In the title text, both screen and tmux are unix programs that help you multitask while working in terminal, and irssi and weechat are both communication clients supporting mainly IRC, capable of working in a terminal environment. Tmux is a newer and apparently more user-friendly project, complete with handy menus and titles, while screen is something of an industry standard, but relatively difficult to use – you need to know what you are doing or read help before use, otherwise you get lost and frustrated.  The same it is with the newer, more feature-packed and user-friendly weechat vs industry-standard, harder-to-use irssi. 
Basically, that one guy is a hardcore UNIX geek who doesn't use any graphical user interface, and in 2078 he still chooses to use terminal-emulation-based tools.
Timing of this strip follows the release of irssi version 1.0.0.
Randall has touched on similar themes before in 927: Standards.
- [Hairbun holding up her palm toward Cueball. A frame over the top border of the panel has a caption:]
- Hairbun: Our team stays in touch over IRC.
- [Megan is looking at Ponytail who is holding up her palm toward her. A frame over the top border of the panel has a caption:]
- Ponytail: Our team mainly uses Skype, but some of us prefer to stick to IRC.
- [Cueball is talking with Megan in a frameless panel. A frame at the top of the panel has a caption:]
- Cueball: We've got almost everyone on Slack,
- Cueball: But three people refuse to quit IRC and connect via Gateway.
- [A black panel with white text and drawings. The main body of text is above a the singularity, a starburst around a circle with two more broken lined circles around the starburst. To the right another Cueball-like guy floats in space with his laptop computer, typing on the keyboard. A frame, that is white inside, is over the top border of the panel has a caption: ]
- Narration: All consciousnesses have merged with the Galactic Singularity,
- Narration: Except for one guy who insists on joining through his IRC client.
- One Guy: I just have it set up the way I want, okay?!
- Galactic Singularity: *Sigh*
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This is an xkcd about why the majority is wrong. ;) 220.127.116.11 16:32, 6 January 2017 (UTC) seirl
F1rst. Jokes aside, wrote you guys something to work with. 18.104.22.168 16:34, 6 January 2017 (UTC)
- See 1258: First and 269: TCMP. Well funny enough you were neither the first to edit the page nor the talk page :-) Thanks for the start, but try to not delete the incomplete tag, but just write first draft or add what you can see is missing. --Kynde (talk) 16:40, 6 January 2017 (UTC)
- Good points for future edits! Appreciated. ♪ 22.214.171.124 16:45, 6 January 2017 (UTC) -Sixi
I find it funny how I'm editing the article, fixing the incomplete parts, then all of a sudden (as soon as I click "enter", I must add), someone's already fixed the incomplete parts, and there was a "conflict with the edit". :P --JayRulesXKCD what's up? 18:47, 6 January 2017 (UTC)
My first addition here, tried to explain skype vs slack and the title text. Feel free to roast me constructively :D Hope I didn't go too deep in Slack, thought most people don't know it and my little experience may help :) Also hope my unix tools explanation won't offend too many people; I'm a happy screen user myself, but it does have quite a bit of a learning curve. --126.96.36.199 19:20, 6 January 2017 (UTC)
Well, at least not ii 188.8.131.52 02:13, 7 January 2017 (UTC)
Well, I think Randal is slightly off, it more goes like this:
2006: The company officially use Messenger - Except all of development ignores it and use IRC
2009: The company officially use Skype - Except all of development ignores it and use IRC
2012: The company officially use Lync - Except all of development ignores it and use IRC
2014: The company officially use Slack - Except all of development ignores it and use IRC
2016: The company officially use Teams - Except all of development ignores it and use IRC
184.108.40.206 10:45, 7 January 2017 (UTC)
- You forgot to add the part where it says that in 2018 they finally migrate... but to Discord. --JayRulesXKCD what's up? 12:54, 7 January 2017 (UTC)
- randall didnt mention discord? smh 220.127.116.11 21:18, 7 January 2017 (UTC)
I find it strange no-one has mentioned that IRC let's you run your own servers, with no 3rd party involved; whereas Skype & Slack both depend upon centralized corporate-owned servers, which are forced to silently comply with surveillance requests without so much as a warrant. That's just unacceptable for many dev groups. (Hence the popularity of apps like Discord.)
I had a lot of trouble viewing this page in Lynx through the Worldgroup gateway on a local dial-up Bulletin Board System. I think it's a problem with my QModem configuration. If anyone can help, please contact me on IRC. I'm usually available in the #Kaypro users room. 18.104.22.168 21:59, 7 January 2017 (UTC)
- Surveillance requests are not be only reason Skype is monitoring your communication. Try to enter url into Skype: it will be visited by msnbot. I don't care why: that's something tool for devs shouldn't be doing. -- Hkmaly (talk) 06:34, 9 January 2017 (UTC)
- I've seen this before, I'd guess the problem is with your 56K modem, during its handshake protocol I'm sure it's going *squeak!* when it's supposed to be going *squawk!*. Just disconnect and reconnect the phone line and make sure no phones are off the hook, then disconnect / reconnect again. That should fix you right up! And remove the AOL disc from the drive, those things are always causing problems. Oh, and sometimes being connected to IRQ or MSN Messenger can interfere, connect with them afterwards. - NiceGuy1 22.214.171.124 05:16, 11 January 2017 (UTC)
So this past fall I remember seeing a bunch of web (and TV?) ads for Slack. You think Munroe got any kickback from Slack for this comic? It's worth noting that:
- - Microsoft launched Skype for Business in April 2015 (as a replacement to Lync). I would imagine that Skype is one of their biggest competitors, especially because Skype is included with Office, and just last month Slack introduced video calling.
- - Last week Slack announced they "invested in nearly a dozen new bot startups to bolster its Slack App Directory" (from VentureBeat). Techy folks who look up Slack after seeing Friday's comic are likely to see this news.
Maybe this is part of an "undergroundy" ad campaign by Slack? After reading the comic I certainly was subliminally thinking that Skype is sooo 2010; 2017 is the year of Slack! Great comic regardless. </conspiracytheories> 126.96.36.199 00:11, 8 January 2017 (UTC)
Dammit, Dave, just become one with the singularity! We have IRC here too! --GranadalandDreamer (talk) 01:39, 8 January 2017 (UTC)
Is there a need to explain "All consciousnesses have merged with the Galactic Singularity", or is it clear enough for XKCD readers? I mean - I've read "The Last Question" by Isaac Asimov, where this happens (including the one guy who isn't ready to go), but I'm old. I'm fifty.
Also "Ch*ldh**d's End" - kind of a spoiler. And "The Heechee Saga".
188.8.131.52 21:14, 8 January 2017 (UTC)
What? No emacs' irc client? -- schnitz 18:31, 9 January 2017 (UTC)