I agree that many threads are needlessly closed, especially the ones with open-ended questions. Moderators assume that because after X posts no objective answer was given, no useful answer will come out of it, and so, for some reason, it's better to close the thread. This assumption is flawed because you never know what the next reply will be, and even if a definitive answer doesn't show up, further replies may shed some light on the topic. I've also seen this happening after one or two inappropriate comments, in which the regular course of action would be to delete those, and not to close the whole thread.
The justifications given don't help either; sometimes moderations mention that "it was discussed" whether the thread should remain open or not. Honestly, this makes it look like this is all child's play. It's better just to mention the reason for closing and move on. Other times the thread is closed for moderation; this is something I've never seen before in any other forum - if you're unsure whether to close it or not, maybe let it be open until you make a decision?
Without wanting to pin anything on these specific moderators, who I believe are just doing what they were taught, take a look at these examples to see what I mean:
Post 1: if that moderator had seen the thread earlier, we'd have missed on DrZoidberg's very good post. Also, I don't get the reason for closing the thread - OP specified that he was looking for an algorithm, not pseudo-code or code in any specific language. What's the problem with that?
Post 2: After that clarification given to the OP, why not let the thread open? Why make it more bureaucratic and making the OP message the moderator so that he/she can then decide whether the thread is worthy?
Post 3: What's the nonsense? If there were nonsense posts, why not just moderate those instead of closing the thread? How does the moderator know that ALL of the further replies will be nonsense?
Post 4: Why does a gossip thread have to be closed on the "General discussion" forum? How does the moderator know that further posts would be speculation about Anthony Bourdain's death? The same moderator even posted an additional comment with a link, which another non-moderating user could've found and posted there; he wouldn't be able to though, because the thread was closed...
My point is that there are many members in PF who give very useful contributions and allow for all of us to learn, and this way of moderating, which doesn't have anything to do with scientific rigor, is preventing that from happening in many cases.