I agree it’s not a TOS violation, but I do think it could potentially be a shitty move to post the ASN from which a specific user is connecting to your service, if they’ve not said it’s okay for you to do so.

If you’re from a small town with a local ISP, associating that town with your first name could be enough to specifically identify you, with the help of yellow-pages directory sites. Even just knowing someone’s state or country is a data point that can be used to narrow down their identity. For the privacy minded, this could be very unfortunate.

I’m not sure why you would be publicly posting the ASN from which a user is connecting anyway? Could you explain the context a bit more here?