If it’s worth saying, but not worth its own post, here's a place to put it.
If you are new to LessWrong, here's the place to introduce yourself. Personal stories, anecdotes, or just general comments on how you found us and what you hope to get from the site and community are invited. This is also the place to discuss feature requests and other ideas you have for the site, if you don't want to write a full top-level post.
If you're new to the community, you can start reading the Highlights from the Sequences, a collection of posts about the core ideas of LessWrong.
If you want to explore the community more, I recommend reading the Library, checking recent Curated posts, seeing if there are any meetups in your area, and checking out the Getting Started section of the LessWrong FAQ. If you want to orient to the content on the site, you can also check out the Concepts section.
The Open Thread tag is here. The Open Thread sequence is here.
I haven't noticed it (literally at all - I don't think I've seen it, though I'm perhaps wrong). Based on this comment, I just looked at https://www.lesswrong.com/users/review-bot?from=search_autocomplete and it seems a good idea (and it points me to posts I may have missed - I tend to not look at the homepage, just focusing on recent posts and new comments on posts on https://www.lesswrong.com/allPosts).
I think putting a comment there is a good mechanism to track, and probably easier and less intrusive than a built-in site feature. I have no clue if you're actually getting enough participation in the markets to be useful - it doesn't look like it at first glance, but perhaps I'm wrong.
It does seem a little weird (and cool, but mostly in the "experiment that may fail, or may work so well we use it elsewhere" way) to have yet another voting mechanism for posts. I kind of like the explicitness of "make a prediction about the future value of this post" compared to "loosely-defined up or down".