Not sure if anyone else experiences this, but I use Google Chrome, and I have noticed that when I exit MMM's website, and then return to it, I need to specifically refresh the web page in order for an updated page to appear. So for instance, I'll read a post with 112 comments in the morning. Close that tab, return to that page later in the day, and it will still be the same page as it was that morning, until I specifically refresh the page.
This quirk, at least for me, seems to only happen when I visit the MMM website. Probably some cookie or internet history issue I have (although it doesn't seem to happen to me anywhere else)
Anyway, point being, just a reminder to check out your browser as that might be a reason why someone might not see any new comments or comments you've recently posted.