It takes a lot of reports to get someone squelched. Not just one. The report system also does not count reports from the same Bnet account as duplicates.
I certainly don’t think the system is perfect, but it beats the gold spammers we used to have. Most of the current forum complaints for squelching are advertising related.
Here is a “fun” recent thread on reporting and automation. Quite a bit of Blue insight into the systems.
Edit - and a really good example of someone trying to blame the report system for their own mistakes. This person made several threads.