Q:

How to cite comment by unknown user disproving Erdős conjecture?

I believe that fedja has disproved a conjecture of Erdős et al. when commenting on my question Almost monochromatic point sets, but I'm unable to contact fedja regarding this. What shall I do? Shall I just casually drop a footnote in my upcoming paper that an unknown user has solved an Erdős problem?

A:

This would not be a first, see arXiv:1909.00177

The citation (which I think follows the best practice) is

[6] Fedja, Communication on the MathOverflow website (2018), available
  online at https://mathoverflow.net/questions/125861

A:

The citation (which I think follows the best practice)
Indeed, that was a good way to handle it :-) The priority here is, as I said many times, to give the due credit to MO and similar sites that facilitate the free and efficient exchange of ideas whenever possible. 
As to myself, my name is neither really famous, nor totally unknown, so I'm neither hiding from publicity, not striving for recognition. Also, most of my answers are based on ideas of other people that I picked up during my 30+ years of mathematical life (which, I suspect, applies to most of us), so the portion of my personal contribution is often hard to determine and even when I know almost exactly what it is, I'm not going to disclose that number. Consider me just a strange part of the outside world that occasionally appears out of nowhere to answer a question or to voice an opinion. After all, in 50 (or fewer) years, that is going to be all that is left of myself (if one considers the optimistic scenario), so why to pretend to be anything else now?
Sorry for that digression into "quasi-phylosophy" but, given the number of times I have had to answer this question in some form, I surmise I have some excuse for stating my point of view on the subject. 
I agree with most other comments in this thread too, so, I guess, it's time to close it and to make it a standard reference when someone gets curious about how to cite "a post by user fedja" again.
Now back to mathematics ;-)

