I actually submitted an alt text request to bsky support! I suggested being able to add alt text after an image is posted, and also the idea of community sourced alt text! That is able to be toggled in image settings.

i'll be interested in subscribing to the Issue if you send the link or number :3

Yes being able to retroactively edit (or even add) alt text would be an amazing change!

community sourced alt text is already a thing: tag it #Alt4Me