Also, do restrict allowed characters when necessary. If one of your apps doesn't allow me to input a particular special character in the password field, don't allow me to have that character in my password.
What kind of situation occurs where you can't input special characters in a password field?
I think in general the advice is that there should not be any limitations on special characters anywhere in the tech stack at all. (Including a broken UI that won't let you input special characters.)
The situation you described sounds more to me like a very poorly written application.
There's one restriction you should do, trim spaces from the start and end of a password (or any input field, for that matter, unless there's a good reason not to). People copy/pasting from emails or Word documents are good at accidentally picking up spaces.
Sometimes the device you're logging in with doesn't have the full range of character sets available. This has happened to me with set-top boxes in the past.
