Trying to consolidate the comments thread on the other post, since its getting long, and is relevant.
There's no 'proper' solution for the lack of usable alt-tags as I see it - there's just too many posts!. If someone decides to fix these in an appropriate manner (no edit flooding!), does a good job at it, and mentions this question as the reason, I don't see any reason why suggested edits that fix images on posts shouldn't be accepted.
I'll personally be adding this to things I fix when I fix other things as well.
However what you're talking about is alt-tags for the keyboard images I think - which apparently works by default. I'm curious - does 
work better?