Indeed.. Putting up just a smiley.. or just saying "cool" or "I agree" or "me too" is considered spamming.
Now of course we're not 100% strict when people make short replies, if they don't do it on a regular basis. But when it's just a smiley, and not even one that was appropriate, (a
after a joke could even be tolerated now and then) I felt a warning was due.
Regards,
Fred