Alt text is a good thing.
When people are viewing LJ through non-graphical browsers, if they come across an <lj user=someone> tag it looks something like "[LINK] someone". If the html produced by <lj user> used the alt attribute in the img tag for the little head graphic, people would see something friendlier like "(view someone's userinfo) someone".
Additionally, on talkpost.bml, none of the little graphics at the bottom have any alt text, so people using nongraphical browsers just see a random bunch of radio buttons. Very confusing.
1. Makes the site more legable for non-graphical browsers.
2. In many graphical browsers, new users of LJ will be able to hover their mouse over the icon and understand what the heck that head thingie is anyway. :-)
3. Follows the 4.01 HTML specification.
4. Additional accessabilty for blind people. (thanks, todfox!)
1. Slightly larger pages to load.
Add the alt attribute to the images on talkpost and in whatever part of the code (HTML cleaner?) that substitutes the lj user tag for the actual HTML.