The language/grammar used here does not fit any of the patterns of spammers making garbage posts to build a post count before dropping their spam junk.
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those users likely used the same password on multiple forums, or, their email has been breached.
For those accounts, i've simply been banning them and asking them to contact support to restore access to their account.
The HPTuner folks are 100% correct. These accounts are likely re-using passwords and have been compromised elsewhere, including possibly their email. There have been many massive breaches with GIANT repositories of usernames/passwords. They then try these on all the places the usernames show up. It actually is far easier these days to use compromised accounts than create bots on forums that have spam/bot protections in place.
I'm sure if logs were looked at, these accounts have either NOT done a password change in a long time, or just did a password change right before they started posting the spam crap. Both are strong evidence that the account has a high probability of being compromised.
Sooooo, just out of good practice, I do advise all of you to change your passwords on a fairly regular basis (at least once a year), use LONG passwords instead of complex ones, AND DO NOT RE-USE passwords.....