I made that experience, too. There are some trigger-words which cause the "spam"-alert. Probably business terms indicating that the user is offering or selling something. Or too many links. Since the spam-filter is not human, it won't understand the real meaning of the post and just releases the jack-out-of-the-box... Can be very frustrating
The computer that was sent from is one of the best protected in the free world. The company I work for spend a lot of money on security software, but I have seen that before on posts I have had nothing to do with, IIRC I've even had it myself.