Private key is split shared so nobody knows full private key including Mercury server, but I would still be careful with Mercury while it is in beta phase.
One issue I noticed is that sometimes wallet does not sync or connects to server and i watched a longer video from last month that showed some other issues are possible:
https://www.youtube.com/watch?v=pL3gQ3C-qPg
Yeah one post from that account, and who knows if he has other accounts like many of people have in this forum.
I think he first heard about Bitcoin on 4chan forum and you would see him in most Bitcoin conferences and meetings, he is not hiding his face anymore behind computer like most people.
Not defending him at all, but guy is obviously interested in privacy, and that is not meh subject for me Dave, maybe it is for you idk.
Anyway if you guys want to continue talking about Alex aka raw_avocado you can open new topic about him and go full force.