People don't typically delete accounts / wipe comments because they are abandoning positions or failing to stand by their comments. They usually do it to protect themselves from online harassment.

From a product design point of view, making user names and post content permanent is asking people to make sure they never accidentally post information that can be used against now or at any time in the future. This permanency solution has a huge downside in that most people are unequipped to correctly estimate what online stalkers are capable of with very little info, especially if they haven't been victims of online harassment yet. This solution also has very little upside -- whatever value you and I gain from someone else's content or username being permanent is worth much less than their privacy and safety.

The alternative solution is to provide a simple set of tools to let users control their own privacy. The upside to this is you can more easily protect yourself. The downside is some, but not very much, software development work. People also have a choice in this scenario, where forced permanency removes all choice.