Forcibly divesting consumer from producer, creating two separate markets where before there was only one, is rent-seeking. They artificially created the conditions that justify their existence, and if they were to stop existing or otherwise stop their practice, the situation would revert. None of this behavior is defensible following any economic ideology except a trivially cruel one.

There is no force, the seller can require name at time of purchase and check identification.

Which requires more effort on their side. The seller have to spend d money to defend its business from rent seeker.

The amount of effort of typing in a name and checking an ID which everyone has on them is inconsequential relative to the benefit.

You will have to convince the people who actually run these platforms that that is true if you want it to be a feature of reality. It seems only you are here speaking in hypothesis while everyone else is speaking about facts of the matter.

What are the different markets? These people just buy up the supply early and resell to the same market.

The markets are at different times and places. Sometimes it is physical (such as on the sidewalk outside the venue). Or it could be a different website.