Requested feature overview description.
Allow guests to search up to 6 tags at once, 8 for users, and 10 for privileged+.

Why would it be useful?
Some users want to do more specific searches. If the strain on the server isn't too bad then that seems reasonable. I use lots of tags especially for image search requests, for example forum #218342 and forum #229446. People often remember many small details, with some ambiguity, and this requires lots of tags in combination.

What part(s) of the site page(s) are affected?
Posts

Related threads (background reading)
forum #3007
forum #154777
forum #207780
forum #252785