For our Perspective projects, we’re using an Ignition IdP backed by a manual SQL database.
Because of a slight mess-up in our account management tools, we created an account with a username that had a trailing space. Trying to use this account caused some bad behavior in the ID provider…
On the good side, if we typed in the username WITH the trailing space at the login, everything works fine. 
On the bad side, if we typed in the username WITHOUT the trailing space, the ID provider seemed to get stuck/broken. 
From the perspective project, it would get stuck in a infinite loop on the “Continue to Sign In” button. When I tried it from the gateway’s identity provider “test login” button, it would return with “No IdP Response Data” and be unable to logout or login to test again. Any further attempts to test that ID provider would just immediately drop me to the response page with the “No IdP Response Data” message.
I suspect some layer in the IdP code is dropping the trailing white space when querying the database and getting a match and getting confused why the rest of the code can’t find it.
I understand this falls in the “well if it hurts when you do that, don’t do it” category, but you may still want to take a look since the IdP was totally borked once this happened, and I had to clear all cookies and restart my browser to get it back to a working state.
EDIT: This was on Ignition 8.0.6