While editing a post tonight I noticed this bug with the tags. There were two of the same tag (windows-7-x64), and several tags with 0 uses but still showing up. Seems broken, unless I'm missing something.
This is temporary -- tags are cleaned up every 24 hours so it is possible for bad (not used, recently destroyed) tags to be in the system for a bit.
Notice that none of those [windows7-hide*] tags are present now.
The (s) tag you are seeing is a synonym, so people who insist on using the "wrong" form of a tag can find it; that tag will be auto-remapped to the synonym.