When a person gets banned here, is that just like a stern almost final warning ? Over time here, I've seen some overly obnoxious trolls get the boot only to come back with a new account name and continue here.

How do you know they were a troll?

Mostly from their post content. Say, for example, someone comes to an outdoor site such as the 24HourCampFire with a post like this one........

"Stand hunting sucks ass. I just cannot sit still for more than 20 minutes and I start getting touretts style fidgeting. I have my new red cat atv and I just ride around busting through thickets like a beagle, hopefully I'll scare up something one day. I need to get my mussleloader fixed through, it doesnt have a rear site.

I have special privliges to hunt my girlfriend's uncle's farm. I go over and boink her and when/if I can get up early, I'll ride that land their house is adjoind to. Only problem is these two dickhead older guys that have plots and permanent stands out on the property. They are TOTAL PRICK C U M PLUGS, they got all pissy cause they said I was flushing out the deer to the next county. I think they are full of crap and just jealous of me and my wheeler.

....or this example of a valuable contribution.....

"I have screwed catmans ole lady catgirl,when he is at work.
I just have not been able to get his kid sister yet.

I can see where those posts would be from someone who really isn't serious about participating in civil discourse.

However, I have seen a lot of people called trolls just because they don't seem to agree with the BSers who post here.