My first time posting here, so I apologise if this seems trivial, but I think it's a major oversight.
Basically, the Unread Posts plugin works really well, and does exactly what it says on the tin, but... the placement of the css code does cause some major issues.
Its my opinion, that by outputting code directly to 1 cell in a table can give large usability and accessibility issues.
First off, for those people attempting to emulate the look/feel/usability of say phpBB so that their users dont complain to much about the move, having the code in the TR so that the css styles can be inherited across all the TD or spans as needed makes perfect sense.
Secondly, when making sites with accessibility in mind, or in my current case a forum aimed at people using screen readers - the ability to output code for the whole TR makes life 1000 times easier for those who are site impaired.
Having seen the revisions for this plugin, i can see where you're coming from in getting a span with the appropriate class in it, but as with many things in BBpress - i think it's time to start moving specific inline css to a higher more modular level (which in fairness is what Wordpress does).
Let me know if i can be of any assistance.