There has probably been spam postings that got deleted.
As for 'unregister' the same as 'deactivate', they are not the same. I think this is how it works (someone please correct me as needed!):
Deactivating only removes the activation from a device. E.g. if you have activated Analog Lab on one or more computers, you'll see those activations in your account. I have not tried the following, but when all activations are removed, I'd think you can unregister the product. You can safely try this to see if you get the big red "Remove from my account" button (deactivations are not "dangerous" since you can just activate again) .
Unregistering or "Remove from my account", removes the product registration from your account, releasing the serial number/license-key for use by someone else.