There is now a way to do so. You can create multiple collections in your account settings and set some of the collections as visible by you only. All the coins you register in those collections will not be visible by others.
Status changed to Implemented(Xavier, 20-Jun-2020, 06:52PM)
Xavier, that's not what was requested, though. The coins to be hidden are part of the same collection. That way the owner still has the benefit of being able to view all of their information in one place without having to switch between collections and only looking at partial data.
I'm sorry that's the only solution I can offer for the moment. You'll need to classify your hidden coins in a separate collection. It doesn't prevent to see all your coins at the same place.
Only if you already have several collections, it would indeed impact your classification.