There’s another thread about this titled avatar or signature or some such. The minimum post was between 7 and 12. I believe it was to stop referral code spam and since the program has ended (permanently as far as we know) the limit has changed here.
If the sale is posted in a thread, openly request that the OP (the original poster) send you a PM. I think that might work. And, if you are looking for a white 2013 S85 in Fullerton in the $33K range. Respond to this thread.
I understand the concern with bots, troll accounts, etc. creating accounts and then harassing others via private message; however, does this just encourage new account holders to post random messages on the forums just so they can perform a reasonable action such as responding to a "for sale" posting that explicitly says "message me"? Not saying I have a good answer to this; just sharing in the frustration.
Can confirm that new members can receive pm's and then reply to them. Still not sure how to create one, but you can ask the op of a thread to pm you and you can reply to them easily. Perhaps it's a mobile limitation?
There isnt anything to "figure out". You need a minimum number of posts before you can PMs members directly, but you can receive PM. This is done by the people who own the site to prevent PM scams by new members, which have absolutely happened and people continue to attempt.
I am not sure how many posts it is as most of the moderators like myself are volunteers and do not control that. I think its somewhere around 10 ish. If you are trying to buy something (which is normally what triggers people to try this) post in the persons thread and ask them in their thread to PM YOU. They can do that.