Excuse me butting in OP.
I’d like to be able to combine tags when using the tags or search page as I believe this would open up lots of UX possibilities, not least being able to easily add Isotope like combination filters functionality - although within a single column so that contextual links were preserved between comments.
In saying that, I am new to Discourse so probably am not aware of all of the ramifications of the above, but I think it’s safe to say if we could be offered more granular searching and filtering, it would open up a lot more client side user configuration options (for example) and take a lot of development load off of the core team.