Below is a sketch of a proposal I devised for handling the problem of rambling contentious meta-level discussions on the main site. The basic idea is to have a list of standardized community-elected meta-comments - comments on non-mathematical matters such as homework, imperative mode, prior work, etc. Each standard comment links to a meta thread on one specific issue. We recommend that users follow the policy that the only comments allowed on such (contentious) topics is the standard comment, i.e. the comment that is currently the top-voted answer in the associated meta-thread (which may change over time as the community grows and learns more about global site dynamics). Any user is free to post the standard comment as a comment to any question or answer - but without any modification whatsoever (note that this implies that multiple identical meta comments posted simultaneously can be flagged and easily deleted by mods without having to worry about editing out additional content in the comment). The FAQ should prominently mention the policy.
As an example, a standard meta comment on imperative mode questions might look as follows
Please be aware that questions posed imperatively are not well-received by many readers ...
... etc, etc
See this meta thread for discussion on this topic; see here for more on standard meta comments.
I think some variation of the above could be quite successful. At the least, this will move contentious discussions off the main site to the meta site. At the best, we can devise standard meta-comments that are polite and accurately represent the diversity of viewpoints in our community (something that should be viewed as an asset - not a liability).
Another benefit is that - due to standardization - these meta comments can be automatically processed, e.g. they could be (automatically) deleted after the thread becomes inactive. They can easily be ignored by users if they have some easily recognized standard form. Further, if there is a way to search comments in the future, then the search algorithm can easily ignore such meta-level text - returning more relevant results. Note that none of this holds true if such metal-level remarks are instead randomly interspersed within comments that also contain text that is mathematical (non-meta). The localization of such meta-level content has many benefits.
If you think that this is a policy worth pursuing, please upvote this question and leave answers or comments with feedback. If you downvote please leave some constructive feedback so that we can attempt to put together a proposal that has some chance of receiving widespread acceptance. Note that the primary goal is to move meta-level discussion off the main site and on to the meta site. For contentious issues the standard comment can in fact accurately represent the fact that that there are various viewpoints, so minority positions needn't be suppressed on the main site if such a policy is implemented. No doubt there are various issues that I have overlooked, but if we all work together to remedy these deficiencies, then such a policy could go a long way to improving the signal-to-noise ratio on the main site.