I also posted a comment (or so I thought) from my Lemmy.world account today. The post button kept rolling for 5 minutes. Checked it on this account.. not there. I am assuming that server is still trying to deal with the recent influx of users/communities/posts. In the mean time, I'm instance-hopping just to see the differences. Having better luck on the less populated ones atm, but I am sure it will get ironed out in the near future.