Is it permissible to name a forum member "Mu'adh ibn Jabal" or "Ali, may Allah honor his countenance," or is it obligatory to suffice with the first name "Mu'adh" or "Ali"?

"It appears there is no objection to being called by the full name of a Companion (as a pseudonym). There is no difference between a first name and a triple name in conveying the intended meaning. There is no legitimate evidence prohibiting naming someone with a triple name in reality, so it is even more permissible when it is for the purpose of a pseudonym. As for the story of the Ansar, its intent was to prohibit using the Prophet's ﷺ kunya, not to prohibit naming someone with a triple name. The preponderant opinion now is the permissibility of using the kunya Abu al-Qasim."