I'm not a native speaker, but I am familiar with the use of "Period." for emphasis. I just happen to think it's stupid. If you have a good point to make, it'll speak for itself, and if you don't, then appending "Period." won't make it any more convincing. That's really all I was trying to say (while ironically using that phrase myself); it seems it didn't really work out due to the behind/following confusion.