Trendi forum is actually a very nice forum and it presents a very cool way someone could earn some cash online. Truth be told, this is one of my best online posting forum and I am actually happy to be a member here especially for the fact that you can withdraw your earnings directly to your bank account without stress for Nigerian members though. And right now, it's the only posting forum where you can get to earn passively when people comment under your thread topic.
But like you've actually said, there are sites like trendi out there on the internet although might not be the exact same policy and payment method but they all operate on the idea that members gets paid for posting quality contents on their forum.
First and foremost, you can try out the beermoney forum which is also a good paid to post site just that you need to be careful and make sure to read the forums policy and assimilate it before you begin posting comments or creating threads there because the administrator pays detailed attention to what is posted on the forum and also the quality.
You can also check out bizdustry, although they have stopped the act of paying members for commenting but I guess you can exchange your points to the VIP members for a very cool rate.