There was no way at the time for me to a) see that I had a second account associated with my email address or b) reset the password for the second account without going through support c) merging the two accounts into one even with supports help.
Indeed. Multiple accounts per email is the most legacy of legacy features, and it's actually pretty easy to not realize it exists even if you work for Amazon. I'm not surprised internal systems don't handle it well. If I recall right, there was a push to get customers to move off it, using site messaging etc, because it was such a pain to maintain.
There was no way at the time for me to a) see that I had a second account associated with my email address or b) reset the password for the second account without going through support c) merging the two accounts into one even with supports help.