You can use address tags to sign up for notifications. https://en.wikipedia.org/wiki/Email_address#Address_tags E.g. if your email is username@gmail.com you can sign up for bugfix notifications as username+bugfix@gmail.com which makes inbox filtering much, much easier.

There are three currently defined headers that I can think of: Subject, Comments and Keywords. Personally, I think I would pick Keywords, but that's me.