When you log onto any web site, your identity is noted (notice how you get a lot of "spam" email)and also where you came from (ie yahoo, search engine, advert click through etc). This is standard commercial technology
They cannot log your identity onto this discussion group - but by getting you to "click through" to one of their monitored web sites then they know who you are,that you visited an apostate web site to get to them, your email address and can locate you if you are surfing from a company etc. From that they can trace you with ease.
Either get a clocking device put on your PC, or don't click through
Jim