I just changed my Oracle ID, in response to a strong hint from Oracle that it ought to be my e-mail address, and not the original ID they had issued me in the 1990s.
I now see my old (made under the former ID) posts, some only a few days old, as having been made by a numbered (six-digit) username, which is not editable. Further, I can't mark any replies to those old posts as "helpful" or "correct" (thereby changing the status to "answered").
Can the old ID be merged into the new one, instead of merely being put into some sort of archive status?
This seems to be an never ending story...
I had to change my e-mail address last year after my old provider canceled his service :(
After reading about the difficulties doing this I asked the helpline how to do this (the right way?).
I blogged the procedure here Changing OTN Notification E-Mail Address (aka Username).
The essential part was removing the cookies before changing the settings.
Cookies have nothing to do with the process. Unfortunately, the exact cause has yet to be identified. Several hundred email change requests are processed per day, so when one or two get missed, the result is a new account.