Recall that if the tag
foo-bar exists, it is impossible to create either the tag
foobar (which differs only in hyphenation) or the tag
foo-bars (which differs only by a trailing "s").
Now, look. I understand why Stack Overflow needs this. This probably reduces the amount of garbage tags that are created by a factor of a lot. Great.
But on small sites, where we have enough high-rep non-moderators to vet every single question that is posted, we don't need this. Not only do we not need this, but it's actively harmful.
Suppose that a well-meaning user with enough rep to create tags (just 150 in public beta) comes by our site about Presidents of the US and wants to ask a question about Millard Fillmore. Well, of course nobody has asked a question about Millard Fillmore, because what did that guy even do? So our enterprising user decides to tag his question with
millardfillmore. Well, our site has been standardizing on properly-spaced tags like
abraham-lincoln, so we would like to have our question tagged
millard-fillmore, but we can't do that without invoking a moderator. (Or using a stupid workaround that involves tagging it with something random, waiting for the zero-use-tag-deleter to run at 03:00 UTC, and then tagging it appropriately.)
I'm not positing this issue as a hypothetical: this has happened over a dozen times on Anime.SE, and we have a meta post over there about it: Fixing tag hyphenation issues shouldn't be so hard.
I don't know what the best way to fix this is (some ideas are posited in the linked post); my inclination is to make the tag-creation-preventer a thing that can be selectively enabled, and only enabling it on sites with lots of new posts per day. A reasonable cutoff might be somewhere near Academia (15 questions/day) or Biology (10 questions/day).
Note: the post I linked mentions some auxiliary issues surrounding preservation of tag wikis; these become moot if we can just fix the damn hyphenation/pluralization issue in the first place before a wiki even gets written.