And in this day and age of ridiculous transparency and whistleblowers everywhere,, who exactly would pay for this post, how much would they pay for it, and for what ultimate purpose?

Why wouldn’t they simply do it themselves?

I have a hard time conjuring up a compelling scenario where an airline, ANY airline, would authorize paying someone $50 / $100 or whatever to post content, be it positive or negative, on chat forums.

Perhaps it’d be more useful to stick to analysis of hard data than dreaming up conspiracy theories?