I don’t know if it’s different elsewhere, but as a mainly-comments poster I’d add (w/Lemmy) that the ‘uploads’ section doesn’t store alt-text (e.g. copy markdown) either. So if you had a reason to use an image multiple times in comments it’s either re-write or copy it from an old comment source. Putting multiple images in a post might handle that better (things other people might actually use too), not so much for niche and/or personal art/technical stuff… and it also assumes a user can still find it.

Also, it probably doesn’t help that it isn’t given a tooltip when hovering over an image in a comment like it does for post icons (average users will only notice the lack of alt-text if they specifically check for it with: 1. view source 2. inspect accessibility properties).

I do try, sometimes I don’t add it especially when it feels complicated to describe and/or I it seems like there’s probably enough words for context already. That and I’m more likely to do it if I made the image. Tenor is an exception because there is possibility of it providing a content description I can copy or at least re-work, but half the time it’s garbage.