BuddyPress.org

Do you mean that it doesnt show as a tooltip or that it doesnt appear in the source code? IE has always been the ugly duckling among the browsers so you cant think that its that strange that it behaves differently.

Btw, I’m not really following what your problem is here, the only problem of a not appearing alt tag is that it might be a bit bad for SEO. I do not see how that could trouble users.