I have the same issue with ports that I must watch on Cisco switches. I checked the unplugged as well, but I still get events every time the interface comes up, and if it negotiates a bandwidth.
I even created a custom field called "dowecare". I have the trigger set to dowecare equal to yes. The suppression is when "dowecare" equals no. The problem, I think, is that I can only set the custom property to "0, 1, true, false", but in the event trigger, I only have the option of "yes, no". So my custom property setting of dowecare = false never matches the suppression of dowecare = no.