If you're not logged in when posting your comment, you're normally redirected to a login screen, and your comment will appear after logging in. Currently, there seems to be bug where the site gets stuck 'saving...' the post for that purpose.
For the time being, the safest workaround is to log in first
and then go to the relevant page and post the comment.
We have reported the bug and are awaiting a fix. Please do keep those comments coming.
And feel free to use the comments box below for testing...