A hard link to an instance is an issue. Instead of depending of a "centralized power", you depend on a "local power". This is, probably, irrelevant in the begging, but later it could cause a drama similar to reddit - like you build a community with 100K people and then instance owner comes to you and say that you must do "X" or leave.
The ideal way to address this would be a possibility to move an account AND a community from one instance to another.