Apparently Michael is an offensive name.

The shortform/nickname Mike is used in a bunch of offensive names - Filter does this sort of thing every year - they're unable to really fix it outside of manual overrides

Doesn't matter how he's using it....how is Michael offensive in any way? 

I have messaged you. This has been an issue for over a year now 

Hi, yeah I’m using it as my first name with my real surname on my player and the combination is being refused 

Hello. Please do not post offensive content here. Any reports need to be made privately. In the future, get a screenshot of the name(s) you want to report and send me a private message.

As far as Michael being offensive goes, how are you trying to use it? Is it the first name? Is the last name somehow offensive?