I was perplexed based on how the OP has presented the case of no possible email or password change and yet, we have claims of user’s account making loan requests but having no idea of these actions been taken by whom is thought to be the owner of the account.
One of the possible interpretations would have been that these were accounts that have changed hands but it’s hardly the case as, these are well known reputable users that have built a name behind there accounts still. Also, these are accounts that spans through 2017 - date and there haven’t been any serious attacks on the forum that I know of that could have result in account compromise. Hence, it’s easy to rule that off.
The possibility of a friend or siblings, I don’t know but, it’s hard to have this sort of fowl play.
Teleporting an account from Bitcointalk to Altcoinstalks, and using a same password. It breaks an important principle, don't reuse password on different platforms.
I recently teleported my account in altcoinstalks. I was required to put the same username there too. So I used the same password there as well.
No requirement to use the same password for the process!
I don't know it is a reason or just a fake one, used by the user to fool us but let's say, reuse password is bad practice.
This brings to light a security risk that might have been undermined on password and email usage on other platforms. It then means, you should identify risk when making associations on a testing platform and that which you have deemed important.
Like you’ve said @tranthidung, just maybe but,
This also brings to light a means to loan approval that could clear doubt which is, signing message from a current address and it becomes reassuring on whom.