These two questions seem to be of the same kind, yet they are acceptable on two different sites. The examples that caught my attention are:
On Cognitive Science, Is there a formal name for the "love" of arguing?
On English Language & Usage, What is a word meaning or having to do with a "love of fighting?"
These are similar enough that it seems as if either could be asked on either site, since both ask for an English, scientific term. Is it fine that both sites answer the same kind of question?
Yes, it is fine that both sites can answer the same kind of question. There is inevitably going to be some overlap between topics in the wide variety of SE sites (do you want your question about the Cowboy Bebop movie on Movies.SE, Anime.SE, or SciFi.SE?) and trying to draw some kind of hard line will be an exercise in futility and frustration.
On the other hand, the poster is expected to put some effort into deciding which site is the best fit for their question; asking about the etymological derivation of some cognitive-science term is clearly not a question about cognitive science per se, and would be much better off on English.SE.
Also, asking the exact same question on two sites is frowned upon; You are expected to pick one site and try your luck. If the community there decides that a different site is a better fit, the question should be migrated.
