Where it becomes tricky is when one is strips away the context isolation. For example, at your friend's bachelor party, some behavior might perfectly normative within context and participants, but the next day when people outside of that context can watch a video of your behavior - you might feel a little shame/embarrassment/regret/etc.
The internet, for better or worse, allows a complete breakdown of context isolation. While the rules of posting on 4chan or HN greatly differ, a person adhering to rules of a given context, will still be judged across both contexts by outside viewers.
The solution here is to create context isolation - which is very easy to do with anonymity.
Not the best solution. I in fact has been saying the illusion that people are perfect is fundamentally flawed for a while now.
moot also made another very good point about total anonymity once before: the reason 4chan (and by extension, other image boards) became such a success is because there is no personal cost of failure, which allowed almost boundless creativity - which is why most of the internet knows 4chan mainly as a meme-generator.