Like at least several other monks (that I know of), I have some "template" information in my signature. With that patch, I'd end up typing my entire node content within the "sig" unless I remember (every single time I post) to move things around.
Is that type of wildcarding common in browsers supporting CSS?
It works with Safari (so KDE variants should be okay) and Moz. Not tried on MSIE.
Perhaps something like <div class="pmsig" id="pmsig-22609">?
Unfortunately this wouldn't work since it would be possible to have multiple occurances of a single user signature in one HTML page.
If we're worried about supporting browsers maybe something like:
<div class="pmsig"><div class="pmsig-NNNN">