I'm by no means an expert in sweave, but I often can help out with such questions, and I know there are a few others here who can too. I don't think that sweave questions are "generally about R and not TeX" although some are but I do think the main criteria for whether a question should be migrated should depend on the degree to which the question is about the LaTeX part of the sweave document or the R part of the document. So I guess I wouldn't support a blanket tag-based migration policy.
Unfortunately lots of R users arrive a LaTeX via sweave, and don't go through the normal learning process of LaTeX. But that often means that their questions are quite simple in principle but with the added complication of the intervoven (interswoven?) R code.
That being said, I would also suggest to everyone that if you're not actually using R and Sweave, that you hang back a bit before attempting to answer such questions here, even if they seem to be fairly obvious LaTeX questions. It would be helpful to see if those of us who are using these tools provide some answers first. Because there are peculiarities of using generated LaTeX code (as opposed to code you write yourself) fixing someone's Sweave generated code as you would a regular document is not always helpful to Sweave users.