Using an account containing a site with a premium theme:
It is possible to delete the account.

The copy instructs the user to cancel active purchases before deleting the account, but it is not possible to cancel a premium theme (it's a one-time purchase).
Reported by a user in 1392647-zen.
When checking whether an account has active purchases, we should probably ignore premium themes.
cc @westi
Also related to #17012
Another case from the forums
@bluefuton it looks like there might be a regression here: In https://en.forums.wordpress.com/topic/delete-my-account-permanently-10/ a user reported being unable to close their account. After an HE removed the premium theme (bought in 2015, so definitely non-refundable), they were able to close the account.
I've seen several users contact us in the forums the past two weeks about being unable to close their accounts, but this is the first case I've been able to confirm that it works after the theme is removed.
I'm able to replicate the issue, using the same testing steps as I'd used when reviewing #27411:
Where normally on an account that owns upgrades you get the prompt to contact support the moment you click on the Close Account option, I made it through the entire flow, including the confirmation step, before getting an error:

Only after manually removing the premium theme from the account using internal tools, I was able to close the account.
Here another instance:
https://en.forums.wordpress.com/topic/closing-account-137/#add-note
Another instance here:
https://en.forums.wordpress.com/topic/unable-to-close-account-3/
Another in https://en.forums.wordpress.com/topic/closing-account-144/
Of note is they were apparently able to delete the site with the premium theme attached with no problem, but still got an error when trying to close the account.
Looks like the problem is on the API side (that message is shown when the deletion API request fails).
@KokkieH are you able to inspect the API response using the 'Network' tab when attempting to delete with your test user above?
I'm seeing this response:
{"code":403,"headers":[{"name":"Content-Type","value":"application\/json"}],"body":{"error":"active-subscriptions","message":"This user account cannot be closed while it has active subscriptions."}}
Thanks for testing that @KokkieH 👍
It looks like Calypso is applying the right logic, but the API endpoint doesn't know to exclude premium themes from the 'active subscriptions' check.
Noting here as an additional scenario to test for a fix:
I just had a case in https://en.forums.wordpress.com/topic/delete-account-2201 where someone had a premium theme subscription on a site that itself had been successfully deleted three weeks ago. So the site deletion with the active theme subscription worked, but closing the account still doesn't work.
Working on an API fix in D31970-code.
Noting I came across a test account with a non-refundable premium theme I'd forgotten about, and when I tried to close the account it worked without any issues, so it looks like this might be working again. Test account username premtestk
I've just deployed D31970-code in r201400-wpcom. This ignores non-refundable premium themes at the endpoint when the active purchases check is made ✅
Thank you!