All three of those look fine, and honestly, if there is a pattern, I'm not aware of it.

It's sorta seemingly random, though I did find something about the commas themselves. The ones I can't see on one particular post look like this: ’
While mine are normally like this: '

I did notice that on one posts, double apostrophes are also three question marks (" is ???), and in one post, the word café has 2 question marks in the place of an e (caf??).

I think it might just be something with my computer, as it looks other people copying symbols from other places (like word or something) is setting it off. In this post, for example, that apostrophe didn't do anything for me and was just a normal apostrophe.