I think some places use monitoring software that actively scrutinises both incoming and outgoing traffic to user-generated content sites such as forums and social networks.

there was one at my former work which would block me from reading my posts if I swore too much!

that is what mangles the formatting your posts sometimes, as well on occasions overloaded proxy servers and gateways in offices (bear in mind at work you are sharing your connection with way more people than in your home).

Not everyone at work will experience these problems as they depend on a lot of variables and different places use different software and hardware solutions for both access and monitoring.

Your employers should by law tell you your usage is monitored if this is the case but have no obligation to give you details on the measures in use. Exactly how paranoid you need to be of monitoring software depends on your employers Internet usage policies.

Lots of places just run this software but don’t really delve into the reports deeply unless someone is not performing well enough in their job or is actively doing far more dodgy stuff online than just posting on a few well-known forums.