![[Welcome to Sensei's Library!]](images/stone-hello.png "Sensei's Library")
I would put it this way:
"Many factual pages or pages on technical topics are in document mode. It is recommended to discuss these in the talk page instead of inserting signed contributions." (this is more or less what it says right now)
"Many other pages are in thread mode, because they contain ongoing discussion. Some of these pages deserve to be turned into document mode, doing a wiki master edit, preferably when the discussion has died down. For other pages, mostly opinionated subjects, thread mode is suitable."
I see document vs. thread mode as a false dichotomy. SL is hypertext, which is richer and includes both. Having said that, pages in either can easily become too large and diffuse. Now that we have forums, most threaded material should actually be threaded, instead of on a single page. And document mode should use subpages liberally.
As for signed vs. unsigned material, I think that that is mainly a question of opinion. And most of the material on SL is opinion, even if unsigned.