I want to play some of the Steam dating sims, but I don’t want to get derisive messages from my Steam friends when they see messages like “Nzall has started playing Tank Dating Simulator”. Do the Steam rules allow me to create a second Steam account that I can play games on I’d rather not announce to my friends that I own them?
Yes, it does. There isn’t anything in the Subscriber Agreement against it.
In fact, you can use the same mobile phone number on multiple steam accounts too.
Also it is clearly stated that you can (and recommended to if you are setting up a dedicated server) create another account:
For security reasons it is recommended that you create a new Steam account just for your dedicated servers.