How do I delete my account? I also disappointed it’s not straightforward to do this. There is not a link in profile settings nor is there anything that comes up in a search.
You do it the same way you do it on all forums
You just log off and don’t come back. Simples 
You have more than 1 post here are discuss.ardupilot.org, Discourse forum system does not allow deletion of account when they have more than 1 post done due how internal system works.
Best and easiest way is like @Paul-H said, set your profile to dormant mode and just do not login.
Or your account can be anonymized and deactivated… you are free to leave with no direct trace