People with experience and knowledge tend to write in a way that exhibits that. I've started many threads here, and when my OP was carefully worded, the responses would typically lead to a coherent and informative exchange of views. This does not always happen but it frequently does. Check my threads to see what I mean.
The other thing an OP can do is to steer conversations back on track by restating the question or by summarizing what's been said that answers it.
In other words, a good thread takes work and some minding by the OP. When people throw a vague question out there and then find they're in the middle of a food fight, that's not totally their fault but there's some need for additional due diligence.