[zackbrown]

The good news is there are plenty of ways to tune for false positives in the machine learning algorithms that underlie spam filters. I'd be surprised if email providers don't consider a flagger's flagging frequency when classifying.

As the OP said, this is just reality: people have different criteria for reporting something as spam. I could even imagine malicious users flooding false positives using bots in efforts to break spam filtering. The state of spam is so much better than it was 10-15 years ago, but it's not yet a completely solved problem.

In short, this person isn't breaking spam filtering all on his/her own--his/her use of flagging may even be arguably justified (if more liberal than average.) He/she just represents part of the problem space.