Not exactly sure how the deleted profiles work. Youve detected 9 in the initial 20 profiles by uid. Ive checked a full profile DB I have from end of last year (data derived by @Piggy), and make it around 16.685 deleted (or not generated) profiles before UID 2473383.
Some of those profiles have posts associated to them, and apparently, the way they are managed was by tying (don't know it it is physical or logical) them to a "Guest" profile under the generic username "Anonymous" (see
https://bitcointalk.org/index.php?topic=15911.msg208900#msg208900 for example), although some still preserved a sort of username (see
https://bitcointalk.org/index.php?topic=67541.msg785785#msg785785).
Theres this to go by:
Deleting accounts doesn't mess up any threads, like
this thread. It just changes to anonymous, with no profile information. Post stays intact.
As you can see here, I only change the username to "Anonymous" on request.