+1 I would also be keen for this sort of feature... I've been fairly active in some of the "wallet" sub-forums helping people recover coins from various wallets due to "broken" seed mnemonics, or wallets being deprecated or issues getting wallets working etc. Because of this, I actually get unsolicited PMs from brand new users who basically signed up just so they could PM me and ask for help.
Then I have to give out email/skype etc to be able to communicate with these users as they only get 1 PM per day etc.
Whatever you are saying tecshare can be done if users can whitelist other users on personal level. Instead every newbie can send unlimited message (with whom you did corresponded.) you can select them (personally whitelisting.) Once you are done with trade then you can remove them or keep them in whitelist.
I really like the idea of being able to "whitelist" individual users, regardless of rank.