Just to let you now.
Any forum’s member has the right to change his/her nickname at any time with no losing their post (profile).
But it seems that the forum platform doesn’t normally support changing nicknames by forum’s users and each time just adds additional user record.
(The next profile contains links to all posts, whereas the post counters ‘see’ only posts written by the ‘current’ name).
One user, three different user records, where the last one (current) covers all previous.