As a matter of fact, I have thought about a site, or perhaps a section in an existing forum. The problem with this is simply offending many people. Let me explain.
I don't know why, but the subject of knives and sharpening seems to quickly sink into an "us vs. them" debate, then flaming, then into angry divided camps with their own websites. And they are intense, insulting entities.
One forum exists because the fighting got so involved that a cluster of members broke off and started their own site. And the spectrum of collectors and sharpeners covers a pre-teen to retirement age demographic.
One 'expert' claims all historic Japanese swords have convex edges despite the fact history books document 800 year old examples. Another polisher still believes that folded and welded layered blade blanks cannot be described using the term 'laminate.' It's akin to being in a room of squalling children.
A public discussion means you put the welcome mat out for a twelve year old with a Chinese knock-off and crock sticks to graybeards with one-off customs costing thousands of dollars.
If you frequent martial arts forums you'll see a parallel. If one guy excels and develops a following, then just as quickly he will also create a following who denounce him.
So here is my odd, cold, counter-productive response to knife related forums.
Until someone with a strong personality, not driven by advertising dollars and owning skin as thin as a rhinoceros is allowed to develop a site where adults can come and share their joy--while quickly deleting noisy bratty trolls who also own knives--a knife and sharpening forum is an absolute waste of time.