This might have very specific utility, but there are also legitimate reasons to provide invalid domain names in posts.
For example when sharing configuration here on meta you may not wish to publicly share the address of your instance. It’s also pretty common to share examples of URL structure against generic or nonexistent domains.
That sounds like a very specific set of circumstances, could you share any more?
This is bad practice, though. Those domains could exist and be something else — or maybe even worse could exist in the future. Examples should use example.com, example.org, or example.net. These are real, resolve, and are intended for this purpose.
The thing about best practice is that the uninitiated aren’t familiar. It’s borderline ivory tower stuff to create friction when posting in the context of the above. Remember that the relative ease of the standard install is such that sometimes installing Discourse might be a users first ‘sysadmin’-type task.
We can’t possibly go about verifying domain ownership before someone posts a link. If they share a config with an invalid domain how do we differentiate between a typo, improperly configured DNS, and a domain which has yet to replicate?
Could you maybe elaborate a little on how a domain checker would have helped with the topic linked above?
The OP doesn’t include a domain, only an email address. It was your response in post 11 which referred to a .com, which incidentally is a valid registered domain - it’s parked at sedo. Had the user specified it and the domain been checked it would have returned valid whois information.
I’m not clear on how your proposed solution would have reduced moderation burden in the topic that you linked.
Honestly this all strikes me as a bit more xy problem than rdd.
Nobody wants to deal with the fallout of malicious behavior, trying to entice users off-site could definitely indicate that. Discourse has a lot of protections against bulk spambot behavior, but this kind of targeted stuff still falls to community flags and responsive moderators.