The 2nd "rule" addressed in the article is "Never put your mask on your forehead".
The reason behind the origins of this rule is unclear. Somewhere, someone said that divers in distress put their masks on their forehead, so don't do it unless you are in distress.
There is no such rule! While it is true that divers in distress often panic and push their masks up from their faces, this is a symptom of panic and not a rule that lets people know they need help. If you are wondering if a diver is in distress, ask them! Also, if you are a diver in distress, signal the people on top by waving your arms above your head to get their attention. This is the accepted signal of a diver in distress. Better yet, carry some type of audible device such as a whistle, or a Dive Alert. Many divers put their masks on their foreheads just for convenience and are perfectly fine.
I do advise a word of caution about mask on the forehead though. If you are caught in choppy waters and are wearing it up there, a wave might just divest you of it! This could make for a very unhappy finish to your dive!