Yeah known issue on our end (not sure if upstream knows about it). The PostComment method does a bunch of extra stuff after actually creating the comment, like sending notifications, clearing your own notifications, etc. I imagine one of those is doing a db query that just takes forever and times out at some point
@Angel@hexbear.net do you have anything out of the ordinary on your account? Do you have maybe 100,000 unread notifications or something
edit: wow, even tagging you causes the issue
edit 2: Do you happen to have the 'Send notifications to Email' setting enabled in your profile?