How do I delete this Forum account?

Just so you’re also aware, the removal of your profile will also result in ALL PM threads you were involved in being fully deleted from both sides, making them completely and permanently inaccessible even to the other users (they also completely vanish from the Inbox). While not strictly required by GDPR as such, it’s something inSided does because PM’s often contain personal data and the Erase User action is intended to zap as much PII as possible.

One of these days I’ll get round to adding that to the marked answer...