A bit of background before I begin: I am a moderator on ELL, and I admit to not being entirely familiar with what is and isn't on-topic here on ELU. I am posting this discussion because I see a trend that I think needs to be addressed, and the following are just my brainstormed thoughts and opinions; they do not reflect official policy of either site. I really want to hear what you guys think, and I'm open to having my mind changed! :)
So, today a question was closed on ELU and reposted on ELL. This is great; the question is actually appropriate for ELL, I'm glad the user was willing to open an account, and I hope they get great answers to their question. The problem I have is not with what happened with the question itself, but this comment that I read on it:
This question appears to be off-topic because it is better asked on ELL.
This isn't the first time I've seen comments like this. Usually they're less specific: "We also have a sister site, ELL. You might find it useful/consider asking this there." And that's okay too; if a question is off-topic here on ELU and you think someone could get a good answer on ELL, of course it makes me happy for people to tell them that! The problem I have is this:
A question cannot be off-topic on one site for no other reason than that it fits better on another.
(Again, above is my current personal opinion, though I do base it on my current understanding of the SE system.)
There are a lot of sites with overlap, and ELL and ELU are one such pair. There have been several discussions on this already, and I don't want to get into what is and isn't on topic on each site; that's not the point. The point is this:
There are some things that are on-topic on ELU. There are some things that are on-topic on ELL. There are some things that are on-topic on both. If a question falls into the "could go either way" category, it belongs on the site it was originally posted to. So that means that the only time we will be suggesting that a user post their question on the other site instead, it is because their question is off-topic on the site they are currently posting it on. It is not off-topic because it would work better somewhere else; it must be off-topic because it is inherently off-topic on the site it was originally posted on. And once it has been determined that this is the case, then you decide "is this question super awesome, and would it work much better on the other site (ELL or ELU)?" If the answer to that question is yes, then you ask the OP to repost (or flag for migration). But the question first has to be off-topic on the site it was originally posted to, in and of itself, regardless of whether the sister site existed or not.
So basically what I'm saying is... Questions should never be custom-closed as off-topic because they are better suited elsewhere. A question is either on-topic or off-topic on a given site, completely independent of other sites in the network. The question you must ask is "If ELU was the only site in the entire network, would this question be off-topic?" If the answer is yes, close it stating the specific reason for which it is off-topic, and then decide if you think it fits on ELL or not. If the answer is no, then the question is fine where it is.
Okay, so I'd love to hear the community's thoughts. Please do keep in mind that I'm not trying to discuss what is and isn't on-topic for either site; we've done that plenty of times and I'm sure it'll come up again. I'm just saying that when something is off-topic, it's gotta be off-topic because you guys think it's off-topic, not because it would maybe work on ELL. Go forth and discuss! :)