Two things to consider based on couple a of comments in your earlier posts.
1) You've been discussing a page within a site, not the whole site. IMO it is much harder to rank a single internal page for a competitive term than it is to rank the whole site. Single pages are more likely to be surrounded by pages that cover another topic, and therefore the surrounding environment is not fully relevant. I've often wondered if that is a factor that counts against a single page, no matter how well it stacks up against the competition in the eyes of a viewer.
2) You mentioned 100 commenters. That is potentially adding a lot of content to the page and possibly fragmenting its focus on the primary search term. Lots of good content and discussion is great for human consumption, but IMO it can dilute the signals an algo picks up and uses to determine relevance for a given search term.
Just my 2c worth based on personal observations.