> Names that are all generated the same way

Years ago you could enter a username and if it was taken you would get a suggested username with added numbers. "Think 'simon' is taken, what about 'simon7889' ?"

Sometime in the last couple of years it autosuggests. word_word_number. For example Interesting_Bus_7217

My suspicion, with zero evidence, is that this was a deliberate choice to enable more botting.