Readers might also be interested to know that anonymity is one of the things constitutionally guaranteed by the First Amendment right to free speech. This concept has been extensively examined in legal jurisprudence for many years. See, for example, https://www.eff.org/issues/anonymity
While it may have an extensive legal jurisprudence, this issue is total separate. The rights protected in the constitution relate to the state.
For example, we have a right to assemble and the state can not deny that. However, a private entity can prevent us from assembling on their property.
In the same way we have a right to anonymous speech and the state can not deny that. However, a private entity (Quora) can prevent us from making anonymous speech on their website.
The reason for this is obvious, would you want newspapers to have to allow the rantings of a raving lunatic if he used a pseudonym to sign it because it can't prevent anonymous speech?
