Take a look at the PS trading forum right now and you'll see that nearly all the posts have HARDCORE or HC in their titles because all the HC players have learned that a number of SC players don't read tags or use them, and they'll get flooded with pointless offers. This alone should suggest that the tag isn't working, because we're all engaging in behavior that circumvents what the tag is supposed to do.
Here's a recent post that did NOT put HC in the title (but correctly used tags, the current solution jsp offers):
https://forums.d2jsp.org/topic.php?t=90504316&f=86As you can see, it got immediately flooded by a troll who was convinced they knew the correct prices despite the fact they were looking entirely at the wrong economy. Admittedly, no amount of separate forums will present trolls from engaging in crappy behavior, but this particular instance would have been prevented by having a separate forum.