I'm developing a website using ccHost and I got wrong behaviour with reserved tags:
I browsed to /media/admin/tags and I wrote a list of "Reserved Tags", like "hi, hello, admin, gamonal, web". After that, I wanted to create a user called "gamonal" and I was told by the system that this username was unavailable.
I came back to Reserved Tags and edited the list, removing the "gamonal" tag.
It wasn't deleted the corresponding row on the database and I couldn't, yet, create the new user.
I deleted it manually and it worked :)