Well I do not know if others face this, but I do.
Whenever I try to whisper someone, and it says "<name> could not be found", I'm in a doubt- Is the name I typed wrong? Is the person offline? Is there no such account?
I would suggest the developers to be specific-
1) If the person Im whispering doesn't exist, or I've typed out the wrong username in /w, then the announcement made to me should be "<name> does not exist"
2) If the typed name is correct and a character of that username exists, but is offline, then the announcement made to me should be - "<name> is offline right now."
That is all I had to suggest, because it leads me a misconception that the person I'm whispering to is offline, and I realise later the spelling mistake in the name.