I have noticed that Mariano Suárez-Alvarez is no longer listed among the moderators and his profile page no longer shows diamond by his name. (I am pretty sure I remember that he was one of the moderators on MathOverflow. In the post on History of MathOverflow he is still listed among moderators as "October 2013 - present".)
I was a bit surprised by this, since I did not notice any announcement of this. (My impression was that if there are changes among moderators, this is usually mentioned on meta.)
Although it seems unlikely, it is at least theoretically possible that the diamond on MO was removed by mistake. For example, this could have happened when he stepped down as a mod on Mathematics - this was announced together with 2018 Community Moderator Election Results (on 14 August 2018).
TL;DR: Is Mariano Suárez-Alvarez no longer MathOverflow moderator?
I apologize if this post sounds as an attempt to stir up a controversy - that is definitely not my intention. I think that moderators play a very important role on the site, so the users should know who are the moderators. In addition to that, if Mariano Suárez-Alvarez indeed decided to retire as a MathOverflow moderator, this thread might be also an opportunity to express gratitude for his service.