Hi Akusala,
Exactly, the lifestyle is not a field of study and, most important, the knowledge that we strive for is not a field of study, but is the knowledge of the ending of suffering. That is something that you can see for yourself working and, this is very important, is indipendent of others, says the Buddha. That means that it doesn't rely on an argument, but on a personal seeing/experiencing that no-one can convince you otherwise precisely because is not argument, but a results given by something that you did or that you don't do anymore. That is why I think (and I think it is supported in the suttas) that self is not something that you have to understand as existent/non-existent, but not-self is something that you have to do due to value judgement and an abandonment. That the work is not to understand intellectually, but to find it where it lurks and dismantle it (As in the famous example of the sand castles), even in our own small way if we are laypeople.
To judge the right knowledge of someone in a forum we should know if they have cessated all or a significant part of their suffering, that is impossible, but yes, seeing them suffer and show malevolence or mockery (since they can be seen in union of what is displeasing for them) for an argument is an indicator of non-knowledge of the benefits of the path, that is different from the intellectual knowledge of what the suttas says of the path that can be instead very developed. When I read a monk that speaks like "only this is true" or mocks people that thinks differently I'm immediately suspicious of the knowledge of the benefits of the path, even if his arguments are 100% correct: I would expect equanimity and a very gentle disagreement with zero mockery. Still, many of the benefits of the path can be lost unless you're an arahant, so we can even see regression and different behaviour at different times (even those that got fourt jhana can regress to sensuality for the suttas, that is a big deal if one thinks about it), it is not all black&white.No matter how persuasive their analysis, if they exhibit unskillful 'speech' then we know that they do not have the right knowledge because the prerequisite of the right 'speech' is just not there. Intellectually, they may be right but the meaning of the teachings has not penetrated beyond the intellectual understanding of the teachings. So, we should take it with a pinch of salt. Is my understanding correct here?
With metta