As to why some posts mysteriously disappear. I know of 2 off the top of my head that have been deleted, both of which seemed to be pretty reasonable and informative, in my humble opinion...

If it's a glitch...ok. If they're being deleted, perhaps an explanation as to why would be in order?

Yeah I just asked this same question in Doug's thread on the 740 vs 940 dress up kit. I am sure I remember James posting something in his iminatable style, has to be a glitch as there was zero reason to delete that or inokiyo's post on RHD cars.

If posts are being deleted / disappearing, and nobody is deleting them (lets face it, only a small number of people have access; admins, mods), then I can only think of two other possible explanations;

A glitch with the server - perhaps it's being updated / restarted at the time of a certain post before mysteriously disappearing. Although this would be in a relatively short time scale.

A mod / admin with correct access could be accidentally editing a members post instead of quoting it, simply by clicking the wrong button.

Just my opinion, as I've personally experienced both of these dilemmas.

I know i'm not deleting posts unless asked to so i'm going with a glitch.

I'm not deleting posts either, but all users have the power to delete their own posts.