When the issues started happening, it
was just locked, but still visible. So the people abusing it changed from posting threads and replies in there, to PMing people who posted threads and replies in there. So the same activity was going on, and they were just doing it in private, which was even more concerning because then if issues arose (which is one of the reasons for the restriction in the first place), there was no longer any visibility to mods as to what was happening.
Even for people who aren't trying to take advantage of anyone, there are benefits to the 30 post requirement. You have 15 posts already (so half way there) and a third of them are in this thread. If I saw you post a request in classifieds, I wouldn't know who you are or what kind of person you are. I wouldn't know if you are reasonable to deal with, are good at explaining your requirements or answering questions I might ask you. Basically, I wouldn't know if I could take on your request and then regret it because you're such a hard person to work with. It doesn't
seem like you would be

But I have offered to help a small number of people and later wished I hadn't gone anywhere near them (so much that I have blocked them so that I don't post in their "help me" threads again before I remember who they are). Taking a bit of time to build up that "this is who I am" by being active in other areas is good for future working relationships.