Using the same 3. Jerboa didn’t support feddit since 0.18 came out though so I couldn’t use it for a while. Liking both thunder and liftoff so far and development seems to progress quite fast. Not sure to which one ill stick with

Ich hatte am Anfang ein paar mal Probleme mit einem Leerzeichen was sich am Ende von username eingeschlichen hat. Eventuell mal das kontrollieren

Seems like you are missing the point a bit.
Because of the open registration policy of those instances and the many users they do not have the necessary tools and manpower to moderate harassing and offensive posts which go against their policy (which they can absolutely set as they want, since it’s their instance) so they block the users of those instances from posting and commenting for the time being.
So it’s not about isolation themselves just for the sake of being and exclusive club of people but because the moderators can’t handle the amount of traffic

Ich hab auch ne Weile gebraucht bis ich rausgefunden hab, dass sich da ein Leerzeichen in den Usernamen eingeschlichen hat und die Seite deshalb immer wieder nach oben gesprungen ist beim Abschicken :D