I think there is always a natural tension between tags and categories.
Perhaps a policy could be used for the new categories by periodically monitoring the popularity of a group of tags.
Excluding the cases where it is immediately clear to us that we need a category, we could consider the creation of a new category as a sort of promotion for a group of particularly popular tags.
Not sure about ide but I vote for environment to be a tag. I have seen from novice to expert encounter bugs which have something to do with how they set-up the environment or how environment got messed up. I am expecting those discussions to show up often.