That's weird. Don't think I've ever played one.
What are these accounts?

Hi,
If your ever suspicious please report,
https://support.chess.com/article/209-how-do-i-report-someone
Thanks I'll have a look into this 👍

Very fascinating observation!
My guess would be they use the same random user name generator, though the top 3 user name generators I found on Google don't give this format as output. But it must be something like that. Maybe there is another tool that is unrelated to user names, like a password generator tool, or maybe a game that provides usernames in this format they have used in the past, that enforced this format as a common practice.
Recently, I started noticing similar accounts in other people's games. I even played one of them on my old profile. There are some examples:
They all have something in common. Firstly, all of them have nicknames written in accordance with a similar concept:
-One of the last four letters of the alphabet (w, x, y or z);
-Dash or underscore;
-Main part (a completely random generated phrase);
-In some of these nicknames, there are also some numbers after the main part.
Also, they all have an International flag. All accounts of this type necessarily don't have an avatar and personal information (first and last name, place of residence). They also don't participate in clubs and don't have in-game friends.
But otherwise, they're playing like real people. Everyone has their own preferences in time controls (someone plays rapid more often, some play blitz). Each of them has their own level of playing. They often give up when they are in hopeless positions. They visit the site without any regularity and do not play for 24 hours a day.
You can find many similar accounts just by using search option. Type w/x/y/z, then "-" or "_" symbol and random letter.
Have you seen such profiles? Have you ever played with them? Share your opinions.