Names on block list are just qustion marks? Like "?????????????" What is that for

I went to check the names on my block list because I though I had seen one of them in a recent match.

The vast majority of them, as in all but one name, were just a row of question marks.

What is that? Were these players banned, does the block list just turn the name to question marks at a certain point?

What is this all about?