Knots useful to the topic matter (climbing, hiking, etc.) are on topic.
Unrelated decorative knots (pretty hair bows perhaps) are not.
Knots for the purpose of bondage are right out.
Also there are two basic types of these questions I see us getting:
How do I tie "X" knot. << I don't mind these, they are useful, and we'll exhaust that list soon anyhow. It's still useful to have them here for a reference. Yes, you can find a million knots online, but what makes a good answer to a knot question of this sort is an answer which is well illustrated enough to learn how to tie it. The other day I had to search through about two dozen youtube videos before I found a usable video for tying a tautline hitch. So here we can provide expert advice through linking to the good web content amongst all the crap.
What's the best knot for... << Good for the format I think, and for getting traffic. "Best knot for a bear line", "Best knot for tying a tarp in wet weather", etc. Here we can provide expert advice directly related, ex: "xxx knot binds too tight when wet"