Works for me on 4.1.7
Wasn't too keen on the bold style and had the same problem the extra line break when changing the <h> tags...so I removed them

I have no idea what I'm doing, but removing the <h> and adding a appears to have sorted it
Code:
<class="subforumlistlabel">{vb:rawphrase threads}: {vb:raw forum.threadcount} <class="subforumlistlabel">
See the attached picture!
Cheers
Nach