It's not always true that the OP's lengthy username gets cut short. On three separate occasions when I have clicked on the user's name on the main page, I have seen the username perfectly formatted. The first time I thought the bug had been fixed but when I clicked again, the username spilled over.
So, I have managed to take screenshots of the last two instances. I don't know why, and I cannot figure how to replicate this fluke but it happens and I had to wait until today before I could get the third screenshot.
2nd time, 26th October
and just now it has happened again, you can tell the screenshots were taken later if you look at the number of profile views, and the rep the OP has since earned
3rd time, 28th October
It's fixed. I didn't do anything but it got fixed. The username does not get cut off when the ratings in the blue box appear.
In order to be certain that the inconvenience was fixed, I looked for usernames longer than 26 characters but failed to find any. It seems to have been an isolated case but was resolved relatively quickly.