That's just the beginning of what a website can tell about visitors.
The admin of this site, can easily get this info if he wants.

It can tell languages installed on the computer, fonts, browser plugins, location settings, time settings and much more.

If the site has a search function, it can tell what people searched for, and if they clicked on any of the search results.

They can get enough information to tie a physical computer to a website comment without reasonable doubt.
And no website based in the USA and most EU countries can refuse to co-operate.

In addition, the NSA, GCHQ, FRA and many others intercepts your communication, as default as it travels down the fibre-optic cables. They can pick up your communication, and most of the information I mention. If it's an email, they can see who the email is from, who it's going to, and the content.

What Edward Snowden revealed, is that parts of this information, for everyone, not just Americans, is captured.
The European spy agencies is sharing some of it with the NSA in America. The NSA keeps the information.
Because the quantities are so mind-blowing, they have built the new data center in Bluffsdale, Utah. The only limitation is that they can't save the information indefinitely. They get rid of it after a certain amount of time, unless it's of interest.

Obviously, no human can read all this information, so they use bots to trawl through it, looking for patterns, keywords etc. If they find something, they can zoom onto that person to the extent that anything he does can be read like a book.

The way to protect your privacy, is to use an anonymizing VPN and if you want to be on the safe side; paying with bitcoin or cash (not your own credit card). They cannot decrypt encryption of 128 bit and higher, but Snowden suggests that if somebody of interest uses that, they safe ALL the traffic with the goal of cracking it as stronger and faster computing power becomes available.

Odds are, that 99% of people reading this, are not of interest to the NSA, and obviously a lot comments that would interest them are missed. But you could also become falsely targetted, because somebody who was under suspicion contacted you.
There have been cases in the UK, of people who just have the "wrong" friends or relatives, or wrote something picked out of context who were awoken in the middle of the night, taken away and interrogated by security services.
It only happened to moslems and suspected peadophiles so far.

Snowden has solid proof that all this is happening. But he is also warning, that since there is no proper control of the NSA, they break their own rules a lot and go further

At the moment, all this is supposed to be tracking potential terrorists.
The problem is that the system is open for abuse. It's also a threat for the future, as a lot of the meta data is saved. Nobody knows who will run America and Europe 10 years from now, or what they might want to use the data to. Consider how Jews in Europe were registered and never thought it would be a problem, just helpful census information. Until Hitler came to power and invaded their countries.