To simplify filtering of Review Board mails I prepend a configurable tag to the subject. E.g. [RB] Review Request: Re-worked flux capacitor 

Christian wrote an reviewboard-dev:
The HTML e-mail change seems good too. I think I'd also be fine with the 
customizable prefix, as long as it defaults to an empty string (since many 
people use it with listservs that may also have a prefix).