Actually, I think that in many of the cases where someone writes someone privately to complain about some of their posts it is because they may want to provide the guy with some insight or correction, but they don't necessarily want to publicly embarrass the guy or point out his mistakes publicly, especially when they are particularly foolish ones. In other words, folks sometimes tell someone something privately because they don't really feel like making the guy look like an ass in public.
If the recipient of these letters doesn't want to acknowledge them, that's his business. And if he wants to publish them for all to see, well I guess he could do that, too, tho in so doing, he might make himself look pretty stupid.
But at the end of the day, people will do what they will.