You have made a good analysis. In short, it is a very improbable use case, but unarguably possible. This is because the reason why you have deleted the user would most likely be present at the time the user wants to come back. How "improbable" this is can be measured by counting this unique case against all the real spam users the plugin has blocked. Anyway, no matter how I justify this behavior, it is possible that the user might need to register again.
Here are some workarounds in order of preference:
- For someone with your technical background, I would recommend just to delete the corresponding record from ^pupi_srs_standarized_emails
- Register with another (ideally non-gmail and non-outlook) email address and then edit it from the account settings
- Disable the plugin until the user registers
Rather than a bug, I'd say there is a feature missing. This could be solved by providing admins a way to browse the blocked emails and unblock them, which would execute the step 1 I mentioned above. I'm not sure if the value it adds justifies the development effort... but I will think about it. Thanks for the clear and detailed question (those are not quite common lately).