It is true that anyone can be traced from an IP address but it is not quite so simple. Firstly they would need to convince a judge that he needs to issue a court order for me to give up an IP address in the first place. Once someone has that IP address they then need to convince a judge to issue a court order to get the ISP to go through their logs and match the IP address to a known user or in the case of someone with a dynamic IP address, the user who logged on at precisely that time. Only then could you use an IP address to identify someone.
Lots of work to trace someone and further consider you really have to have slandered someone seriously for any judge to allow this to go further.
Although this is a Rumor Mill, I dont think I would worry about losing my job over any posting.
I have had my hands slapped by Dannys Boys a couple times for not being "courteous" to some Morons, so I think they keep a good handle on what is allowed.....