[@_ck_ Participant 18 years, 3 months ago]

Actually, I just realized there is a cheat way to do zero extra mysql queries and link to the profile.

<td class="num"><a href="/forums/profile.php?id=<? echo $topic->topic_last_poster; ?>"><?php topic_last_poster(); ?></a></td>

untested but should work in theory

This will just use the stored last posted id # instead of forcing bbpress to lookup all their meta data and profile link in the database.

If your forum uses permalinks, it will just rewrite the url on display.