I started playing about a month ago on a MeseCraft server (not Mesecraft.com), and noticed strange islands in the sky.
I LOVE sky islands, so I built up there and started building my base.
Later on, I found the Tome of Portals, and built a Nether- and then a Portalstone Portal, only to find that I already was on the cloudlands the Portalstone Portal would have teleported me to.
I think that broke immersion a little. I digged deeper into it and found out that the cloudlands mod can be configured to have a higher spawn rate, which I think should be added up closer to 400 or 500.
Currently, it is IMO too easy to accidentally discover them in the very beginning when they should be later game.