Since I've discovered the new sport of retagging (and others have too it seems, with many recent retag requests, and tag mergers), I've had some time to think about this.
Perhaps in cooperation with black listing, or perhaps more with the tag synonym suggestion, I too propose that tags can be defined, i.e. have a very short description (editable), for cases of ambiguity.
For example, [delegate] could be defined as "Delegate type from C#", where as delegates would be "general delegates". There are many such cases
The idea would not be to restrict, but to enrich, and guide in the ever crucial tag selection process. The definition would appear next to the selection (there's a big empty space there, after the number of times a tag was used), or on mouse-over (if that's easily doable with a list) at tag creation time. Other places, like on the tag page, are also good.
Editing would be for 10k+.