You might think you are invisible, but in all reality, they're probably logging your every move. Trust me, much more than you can imagine can be logged/captured. I manage web filtersingfor a large corporate environment.
In the bigger shops, it's not the IT guy that makes the decision on this stuff. It's the legal counsil, HR, and CSO (cheif security officer). Even though I have all the knowledge to bypass it, I surf with caution while on the job. Changes are logged, multiple systems log traffic, so anything questionable will used against you if a legitimate reason is found.
By the way, setting up an SSH listener on 443 might not work. The really good filters have caught up on this practice and will still stop it if properly configured (for example, Palo Alto boxes!).