Sometimes the proverbial excrement hits the fan and I need to reinstall the OS on a laptop or something. This isn't an issue.
Normally, I follow the following procedure:
- delete the computer from the AD
- reinstall OS
- set the host-name to match the old setting
- rejoin the domain
I'm wondering... what would happen (if anything) if I skipped the first step and just rejoined the domain with the same host-name?
Nothing at all. That is perfectly fine. As soon as the machine joins the domain it sends in it's hostname and renews/sets its trust. This would only be an issue if two machines had the same hostname, the machine being rebuilt would join the domain, where the old one would get kicked off (it would invalid the trust).
TL:DR; Nothing, this is fine, you can rebuild without deleting it from AD.