I had a problem using this gem and Mysql. When I had a tag named "historia" and another named "história", if I tagged an object with "historia" and searched it, I was getting both "historia" and "história". So I solved it.
Please tell me if there is something wrong with my pull request.
Fixing tags search when looking for some latin characters
I don't think that your pull request is necessary. If you just change the collation on the name column in the tags table to utf8_bin it works out of the box