You know when you want chat bubbles in your fic on AO3. And you know that probably thousands of other fics already have them. So instead of reinventing the wheel and coding them up yourself, even if you technically know how to, you ask someone if you could have a copy of their workskin, or you find one of the probably hundreds of guides to that exact thing that are right there on AO3, or you copy some code off, like, Anywhere On The Internet that has something that looks like what you want or—
No, I didn't do that. I got into a CSS hyperfocus and spent hours writing them from scratch, of course I did, wouldn't be me otherwise.
(Minor spoiler warning for Scorn and the Saint-Maker [link to AO3], but then again, there's not really anything here you wouldn't expect from me OR THEM, we just haven't got to that part of the story yet)
(I'm happy with them though, I think they're very pretty, and above all the markup they demand is (1) as simple as I could make it, (2) logical enough that I could also quickly hack up a script that'll convert a reasonably-formatted bit of text from Google Docs into it; and (3) makes it so that things are readable and understandable as a chat conversation without creator styles on.)