Admittedly, Inner Dialogue’s a little weird in this regard. I don’t have alt text, but I usually have a few sentences at the bottom of each page that serve the same purpose. I mostly use that space to add a second punchline to the comic, and sometimes the “bottom text” joke ends up being funnier than the actual comic (in my opinion).
One time I abused that bottom space to tell everyone it was my birthday, but that was extremely necessary and important.
I’ve been on the fence about whether I can say those messages are an “official” part of the page. So, for those of you who have alt text or something like it: Does that count as part of your comic?
The thing here is author intent. Alt text is definitely part of the comic for XKCD. My comic originated elsewhere, so having alt text on some pages is a bonus feature. Mostly I just give background information that's separate from the comic's intent. If your alt text is part of the story or part of the joke, and you want it to be, it's part of the comic. If it isn't, then you're having fun anyway.
I would consider it part of the comic, because it's, well, part of the comic.
That said, I've never used them. Seems silly or gimmicky to me. That's not saying they ARE, just that I didn't see a use for them for my own comic. Not to mention having to THINK of one for every page. Heck, I sometimes struggle for a page title. I also find them a little distracting/irritating. Again, just an opinion. And if the comic is every made into a book form? Would they appear in small print at the bottom of the page?
Normally, one would want your comic/story to make sense as a stand-alone without having to insert extra material to fill in the gaps. Like... I've heard it said "If you have to go back and explain your story for people to follow it, that's your mistake as the author" (not that the extra trivia isn't fun or helpful, but ideally, the story should still be clear and enjoyable without it)
If you put necessary information in your ALT text, I guess that's making it part of the story, because without it, your story is incomplete.
In any other case, I'd consider ALT text/author notes/ etc...just fun little bonus sprinkles on the cake, instead of part of the cake itself? In the end, though, I guess it does come down to author intent.
I can't really consider my ALT text part of my comic, because sometimes I put dumb jokes/commentary during a serious moment and I'd hate for that to be branded as part of the story...yeesh.
Authors notes I'd say I tend to overdo a bit (understatement), but then I normally tend to read others too.
I'd say alt text is fine for little hidden jokes, and possibly page numbering, or other superfluous stuff, but anything important? No. If it's some important point to make put it somewhere clearly visible, page, authors notes, whatever. Otherwise the only way people are going to see it is if they check for it, or just happen to hover over the image long enough.
I have seen more than a few make good use of it for extra jokes though, but ultimately it's not all that necessary when there are better alternatives (except if it's something you want to keep semi-hidden!)