Can't Access Certain User Profiles
I'm not sure if it's because the user name has periods, or because it ends with a period, but I was trying to access the user profile here: https://www.duolingo.com/Christopher.C.H. and it keeps giving me an error. Maybe someone from the dev team could have a look.
You are right. The confusion arises since the user appears as Christopher.C.H. in the following list of the OP. It's probably a change in username but directly clicking on the user's profile in the following list results in a 404 error due to the broken link (as link is created with old/incorrect name).
The problem appears to have been solved. I'm guessing it was indeed a username change, but there is some kind of caching system in place that displayed the old user name (and link) in the "Leaderboard" on the right. It now displays the correct user name and link. Thanks for checking!