TL;DR Allowing editing without deleting in mastodon would be a significant benefit to the blind and sight-impaired community.
Thanks to @n0btc bringing it to my attention I have tried to be more mindful of captioning my photos. It seems an important effort that only works well if we all try and do it and be considerate. I absolutely support this.
The problem is I have decades of not doing this and posting memes is very much automatic at times. I see something funny and I post it a few seconds later with my own 2 or 3 word blurb. Problem is I often forget to caption the photos.
Now you can argue I can just do delete&redraft, and this is true, in fact if I catch my error before the post has any activity this is what I do. But I find most of the time it is hours later or even days I forget. So its far too late to do that without loosing all the boosts and orphaning any comments. Not to mention it would annoy the whole fediverse to see the same meme or photo pop up in their feed twice, hours apart. People have even contacted me about that complaining because they see it as repost spamming not realizing it is a edit.
The solution I use is to just add a comment with the picture description when I realize. But I'd imagine this is very inconvenient for the blind & sight-imparied as they would have to look through the comments before they even know if there is a description or not.
This is why being able to edit-in place would be a huge help to them, we can add technical corrections we simply wouldnt otherwise add. The easiest solution I could think of is to keep a revision history and otherwise allow it.
Anyway, hope @gargron considers this as a feature soon.