is all LJ offers on this, and it doesn't mention ALT either way.
I think you need to add a couple of sentences about how to use the ALT tag for those of us who are low-vision and need the text to explain the images we can't see. Adding the ALT tag info to this FAQ about how to post an image would help a lot.
I don't know if I'm posting this in the correct spot; the "help" I got from LJ was extremely cryptic when it sent me here.