I want to find somewhere that I can collect information that's important to evaluating the quality of an item (probably something niche but useful) and learning about good sources to find this item and things to look out for from vendors, such as misleading marketing lingo.

For example, I'm looking to buy an air purifier and I see many different prices and similar terms. It means I have questions like what's the difference between 99% and 99.99% particle filters? What's the difference between HEPA and HEPA-like?

But I wouldn't expect this is something that would require a full subreddit about that particular item since people don't go to market for them very often.