There is a growing number of Stack Exchange communities. It happened a few times, that I was not sure, to which community my question suited the best and it also happened, that I totally forgot about a community and I asked a question in the wrong one.
For example I asked a Raspberry Pi question on Super User, although there is a Raspberry Pi community.
I think it's possible to detect from the title and the tags, to which community a question suits the best. If it's the case, that the user is about to post a question on the wrong community, a hint could be displayed.
Another idea to approach this problem is to implement something like a wizard. I imagine this like a text field, where you can enter tags. Then the most suitable community appears.