Over seven years of membership of ASIF, I've posted 55 times. (Up to the beginning of this year, it was only 18 posts.) That's because I'm here to learn, without the background knowledge to be able to say much. This year, there have been several threads where I felt I could offer a meaningful contribution - hence the tripling of my post count. The posts I'm really interested in are the ones which supply evidence, and those that make reasoned, professional commentary on that evidence.
As others have said, a few posters like to jump in with pet theories, and then stay for endless arguments about them. Normally I scroll through these, but it does take time that many professionals don't have.
I don't know the details of Simple Machines Forum software, but I've been involved with similar in the past. Is there any function for making certain threads "read only except by invitation"? If so, a thread like "2020 Sea Ice area and extent data" could be split into:
2020 Sea Ice area and extent - data (read only)
2020 Sea Ice area and extent - discussion
In the first thread, posting would be restricted to those people who have proved that they can provide facts, and discuss them in a sound, sensible manner. The second thread, open to all, would be for everyone and everything else. Extra work for admin and moderators, but it would cut down on the number of complaints, and provide a clean "reference" thread for scientific professionals or journalists who want to look up the facts.