I disagree that Buddhism SE should be split into different sects for the following reasons.
Firstly, the fundamental doctrinal core of the different sects or traditions are the same.
In Christianity, all major denominations accept the Nicene Creed. In Islam, all major sects accept the shahada.
Similarly, all major Buddhist schools accept the Four Noble Truths, the Three Marks of Existence, the Noble Eightfold Path, Dependent Origination and the Three Refuges.
Secondly, certain sects or traditions may have additional philosophical content that other sects or traditions do not accept, but are nevertheless ultimately not contradictory to the fundamental doctrinal core.
I've made some analysis of this in this answer.
Thirdly, there are definitely many questions that are tradition-agnostic or sect-agnostic. I think more than half of the questions we have on Buddhism SE are tradition-agnostic or sect-agnostic.
Fourthly, there are some hybrid experts both on this site and those outside this site (who are used as references), who can cater to multiple traditions simultaneously. We would benefit from their diverse and cross-traditional perspectives.
I would completely agree with Lanka's proposal here as the solution to your problem:
In the past we discussed writing a short sentence in the beginning of
an answer, to state which tradition the answer belongs to. I myself
forget to do that sometimes. I guess we could be better at stating
that to avoid confusion for new-comers.