Newly proven account triggers suggestion to track someone I already track

Here's what happened:
1. Followed a user on Twitter who had not yet proven their Twitter identity for Keybase
2. Tracked the user on Keybase
3. When they proved their Twitter identity on Keybase, I received an email with the subject, "@ on twitter (your friend) just signed their account," containing the text, "You follow @ on twitter, and now you both have public keys on Keybase, with signed twitter connections. This is cryptographic utopia! You should consider tracking them, which commences a signed record of their public key and identity announcements. ..."

The problem is, I already track this user on Keybase. Before sending these emails, a check against the list of already tracked users should be performed.

Trace the account-proving flow that sends the Twitter identity email and inspect how existing Keybase tracking is represented. Reproduce the sequence from the issue, then verify that users already being tracked no longer receive the suggestion email while newly tracked users still do.

Written by the indexing model from the issue text.