Brief bug summary: When trying to choose a main character at the player ranking, there are multiple issues that I noticed.
1) Some characters can be added as a main character, even though they are not level 10 yet.
2) The character sprites of the classes that can be added are broken, while the correctly functioning sub-level 10 characters have the proper default blank image.
3) You are unable to add characters from the Reboot world as main character. Both my Reboot characters are above level 10 (151 & 58), but they have the same broken sprite as mentioned in point 2 and nothing happens as you click on them.
4) You are unable to add characters from the Luna world as main character. These characters have the default blank sprite and you will get a popup stating that you can not add them as main character because they are not level 10 yet, no matter their actual level.