All these answers and comments below have been a truly learning experience for me. I was told a lot of useful and important things, for instance that I can write an answer myself, that I can upvote or downvote, that any comment can always be deleted. Now I know, thank you. Pity that the only thing I still don't know is why certain comments get deleted and some not.
Should anyone try to tell me that content counts, I recommend comparing my deleted comment - which I described below (and which was removed after just a few hours) - and those two comments that are still there after almost 2 days:
I skimmed the blog. Wow, just wow. and
+1 for including a short and long answer. (we all know that +1-type comments are highly recommended on stackexchange)
(I guess further downvoting my question will give me the lesson I deserve.)
Why have moderators removed my comments (and a few others) here in this question?
John Rennie said there (this comment is now gone) that the blog the question was based on is nonsense and to justify his opinion he linked another question about the speed of gravity. I pointed out that the 2 top scoring answers to the question he referred to give no evidence to support their claim about the speed of gravity being c, and that one answer showed some links and commented that the dispute is at best unresolved.
Why was it removed?!
And to prove that moderation follows weird policy regarding answers and comments - the top scoring (18 votes now) answer to the question I am talking about is this:
Short answer: No. Long answer: Nooooooooooooooooooooooooooooooooooooooooooooooooooooo. Moral of the story: Gravity and EM are two very different things that look similar to some people because they both fall off like 1r2. Be careful what you trust. When someone makes a claim like that, check their references. If there are no references, ignore it.
How come this is considered a valid answer while my comment is considered invalid?
P.S. You know, I'm from Poland - a country where people have learned all too well what censorship leads to. I have never suspected I might be the subject of such practices in the so-called "free world" - be it US or the Internet. It's just so sad ...
EDIT: Should someone think I am a lunatic or otherwise obsessive, I will show a better example of what I mean:
Sometime at the beginning of my presence here at physics.stackexchange, I wrote this answer: Do photons occupy space?. It's actually only a quotation that experiments show that photon seems to have real spin. After that I not only received immediate downvotes, but also a number of derogatory comments calling me naive and such. When I responded accordingly (but not overtly), my comment was removed, while the original offensive comments were left intact. Only after I asked why moderation was unfair, the other comments were removed too. Apparently, moderation didn't mind offensive comments as long as they supported the "right concepts". (Notice, I didn't develop any lengthy concepts or theories considered non-mainstream. I only pointed out to a fact provided by scientists from regular university). Since then there were a number of cases where I could see that certain comments are not welcome. So this time it was just too much and I decided to react.