You can delete your LFS account on the main LFS site but I don't think it deletes your forum account, you can't usually delete them as it would mess up all the old threads due too all the missing posts from deleted accounts.
The account could be deleted with the posts remaining, but stripped of the username, avatar and signature and all other personal info, commonly implemented by assigning them to the "Guest" or "Anonymous" user.
yes that is standard vb behaviour upon deleting an account. Its posts would just be made by Guest then.
But standard for LFS account deletion (requestable through your account details page on lfs.net) is a deletion of everything that is publically visible. So the LFS account is removed, all related LFS stats, and also the forum account and all posts by that user are pruned. Threads started by that person are removed entirely.