First of, this thread belongs in Meme Research.
Secondly, I had considered making an xkcd article too some time ago. I felt that it would have been a good parent entry for any memes originating from the comic but not as an article about a meme by itself.
You see, there is certainly no definite and final description as to what makes something an internet meme. The term is very loose and viral material such as the xkcd comics can be as much of a meme as classics like Pedobear and Rickrolling. For this reason, our site had to draw the line at a certain point and one of the things beyond this metaphorical line would be webcomics as they can be interpreted as just another form of public media (they're basically just comics posted on the internet). This also applies to other similar forms of media (i.e. fan fictions) which also needs no documentation on this site. So sorry, but xkcd cannot stand on its own as a meme article.
Though, going back to my point of it being a possible parent article, the only reason I haven't made one is because as of now, and as was the case those many months ago, we have only two documented and confirmed memes originating from xkcd, those being Roller Coaster Chess and [citation needed] (though originally a part of Wikipedia's fact-checking policy, an xkcd comic started the trend of using the phrase elsewhere). I just don't feel that there are enough sub-memes yet to allow xkcd its own parent article.
So yeah, now that I've made my point about that, I'll move this thread now.