Title text: Do I get to remove letters entirely? Or just rearrange them? Because the 'k/c' situation is ridiculous. Look, we can make out whenever. This is *immortality*!
This comic is mainly a joke on the traditional pick-up line that goes: "Baby, if I could rearrange the alphabet, I'd put 'U' and 'I' together." Terrible? Yes.
However, in typical xkcd fashion, rather than continuing with that tired pickup line, Cueball jumps at his hypothetical chance to rearrange the alphabet and fix the English orthography. An orthography is a standardized system for using a particular writing system (script) to write a particular language, including rules of spelling. The English orthography happens to be one of the deepest (that is, most irregular) ones around, since almost every sound can be spelled in several ways, and most spellings and all letters can be pronounced in more than one way, and often in many different ways.
So faced with this opportunity, the hooking up could wait. Restructuring the alphabet and creating a sensibly regular English spelling is the chance of a lifetime, and would make history.
 Title text
"The 'k/c' situation" is about the use of the letter 'c'. It doesn't have a unique sound, and most often make a 'k'-sound or an 's'-sound. Combined with an 'h' it usually makes the 'ch'-sound in chair, but also they often sound like 'k' (character), and in not too few cases they even make the 'sh'-sound. (a list)
So a reasonable change Cueball might make is to get rid of 'c', and come up with a letter that exclusively sounds like the 'ch' in chair ([tʃ] in the International Phonetic Alphabet).
- [Cueball walks up to a girl sitting at a bar]
- Cueball: Baby, if I could rearrange the alphabet, I'd forget about you in a *heartbeat*. I'm not gonna waste my one chance to help the mess that is English orthography.