The reason the avatar is the same is that the e-mail address is the same. Based on this and other factors, they are the definitely same account/user (now merged). I agree that the system could make it easier to spot this, but there are some complications:
- we obviously would not want to allow account stealing just by knowing the e-mail address (mine/Jon's aren't exactly secret, for example)
- it isn't really a huge problem for unregistered users
- it is already easy enough for us to search by things like e-mail address to relocate and recombine accounts, but again: unless one of the accounts is registered this is a bit like taping smoke back together...
- Jeff/team would have better access to numbers, but I suspect that the volumes of dup accounts would make it very high maintenance, unless we only reported on duplicates past an arbitrary date, but again: unless one is registered it isn't necessarily useful
So all things considered I'm not hugely sure it is worth changing much, except perhaps locating obvious duplicates where there is a registered account involved.