"when I post a comment or reply today it doesn't appear that it posted - I accidently replied to a message six times earlier because it didn't look like it posted"
"just now I deleted a double post because my browser is not updating after I post and I posted it again before checking by reloading the page"
"hit the 'post reply' button and nothing changes. reply text still in window and cursor hovering over 'post reply' button"
These were followed by many "ditto" and "same here" replies.
FWIW, the same experience happens to me, even after clearing my browser cache. In the Quick Reply window, I type a reply. I click the "Post Reply" button, the animated icon shows that it is sending/loading, then it disappears, but the reply box is still there with my reply in it and it doesn't appear to have posted. But if I refresh the browser, the reply has indeed posted. I can easily see why someone might try to click Post Reply again, thinking that it didn't work for some reason.
Is there something I need to do after the upgrade? I followed the upgrade instructions exactly, as I always do. Or is this just something where the users have to force a browser cache clearing or wait for it to expire?