Right now the pending user approvals / duplicates process is less than great. Duplicates doesn't look across a wide enough array of fields (so it overreports false positives) but also seems to miss actual duplicates. I'm not sure how best that should be handled, but as a bandaid, Site Admins should have the ability to declare two profiles duplicate, and merge them. I would like this to be possible even if they are both user accounts ideally.