Robert has made clear that, at least at this point in time, we should aim to accept questions from all engineering disciplines and not restrict our scope based on the existence of other engineering sites—EE.SE being the main example.
Russell McMahon points out in the same discussion that we may be doing harm to our community in its early stages by not dealing with this overlap in a consistent and efficient way.
I agree with both of these positions but it's far from ideal to hold scoping discussions on the comment thread of a question. So when I see a comment like, "this belongs on EE.SE," I would rather not engage with them. I think these comments are not constructive but I don't want to start flagging them without a policy in place.
Are comments directing users to ask their question on EE.SE constructive?
If not, then our policy should be to flag and delete them.