Thanks for posting!
The warnings that post refers to exist outside user notes. When a moderator writes a personal message to a member, there is a tickbox to make the message a warning. When selected, the message is styled differently so the recipient knows it’s a warning. That action is logged in the review queue and also shows up as a user note. This is good!
This is the only automatically generated user note I am aware of. I agree it’s problematic and we already have been talking internally about preventing it from being added to user notes, or having it automatically removed again if a moderator decides it is not spam.