My personal thoughts on this:
1. This is a private website and ultimately the moderators and management can chose to allow or not allow posts on watch value - it's really down to how users behave and whether they chose to take their posts elsewhere. It's a very difficult subject because it is notoriously difficult to patrol, and even if well managed, it generally invites members outside the community to post non-value added queries, trolling, and related unpleasantness. In a sense, not allowing such topics is a relatively blunt instrument way to manage content; I'm sympathetic.
2. I'm truly amazed how strongly Patek Philippe as a company pushes this subject onto its client base. Quoting the most recent Patek Philippe magazine: "The remarkable investment value of Patek Philippe watches was proved once again during Geneva's end-of-year auctions, when Christies's dispersed the third part of a single-owner collection fetching some US$3 million. This amount, achieved for ten watches, brings the total for thirty watches now sold from the appropriately named "Connoisseur's Vision" collection to over US$19 million...". (emphasis mine). I'm not too sympathetic; this is the manufacture!
3. It is very reasonable that someone spending quite a bit of cash on new or vintage watches wishes to feel they have acquired an asset rather than a plaything. It is a slippery slope then to speculation; which is forgivable but...well, see point 1 above. I'm sympathetic.
4. While expressing sympathy to both sides is not particularly helpful, I think a possible compromise might be to trial a forum for specific auctions. It would allow the main fora to be clear of these types of discussions and create instead a single area for auction discussions. Yes these would touch on value and results but this would be a hopefully manageable discussion specific to the auctions then at hand. I would have thought it would be in the auction houses interest to encourage such discussions and there may even be some commercial links that could be established with them similar to what is achieved with some manufacturers. Having purchased at auction in the past, it certainly would have been helpful to be able to draw on a community expertise when thinking about some lots.
So to me it's not the end of the world if we can't discuss such matters but they are interesting; perhaps auctions are a possible way to focus the discussions.
All the best and I hope I'm not locked out of posting this!