Thanks for adding these back. When I launched my site the other day, the first question from one of my transferring members was “we can’t use spaces in a username?”
The instructions are incredibly useful and they’ve been turned on for my site. This is feedback for the whole team that forum usernames, the way Discourse does them, are not necessarily intuitive to those used to older forums that can use spaces and special characters, etc. Instructions are critical to avoid losing new member interest.