This search will reveal a ton of questions with
c# in their title, which are also already tagged as c#:
Currently there are 93,199 such questions. In rare cases it may be important to leave that in the title, as it makes a difference, but mostly it's redundant use of tags.
SE rules explicitly discourage the use of tags in question titles without good reasons, yet there is no pop-up message when there are tags detected in question title, which is kind of strange.
I see there is already automatic removal of tags in brackets, but not in braces, or without any kind of separation. So there are still tons of questions when the use of tags in titles is redundant. In some cases, though, it's fine to include them in the title, like when otherwise the title won't make sense.
I propose to create automatic tag detection in question titles in form of a blue pop-up balloon with a link to the rules section about unnecessary inclusion of tags into question titles, reminding the poster to make sure it's absolutely necessary to have tags in the title.
UPD: I just found out there might already be a system that detects tags in question titles, as per this comment from 2010. I bet that could be used to activate a notification saying "Make sure you're using tags in title correctly".