I'm not a moderator, but I doubt they'll change the requirement and I'm not sure they should, myself. There are various reasons why sellers might not want to sell on this forum in particular, but a big one is that many who post here sell on
ebay. If you click on a member's name, it will show their
ebay user ID (if that member chooses to make that available) and a link to their listings there. It kind of accomplishes the same thing, and most members just do it that way instead.
If you sell on
ebay yourself, there's a place in this forum's account settings (I think) where you can input your
ebay user ID and make them visible to other members. But, it's a good idea to keep posting here in any case. Firstly it's good practice to actually participate, learn, and help new collectors, etc. It's why the forum exists to begin with. But if you're looking to sell anything and want people to see your
ebay listings, having more posts will keep your name more visible and more likely to be clicked on. If you want to sell specifically on this forum, people will be wary of buying from someone with a low post total who never participates. They won't feel they know them or trust them.