For pesky trailing slashes at the end of URLs,
example.com/ are equivalent. What about subdomain homepages such as
support.example.com/? Is it the same rule?
The domain name part is processed seperately the "path" part of the URL. Subdomains are treated the same way as their parents by the web server (in fact example.com is a subdomain of com).
This is maybe easier to demonstrate in cctlds - example.co.nz behaves the same way as example.com - even though its a subdomain. ( www.example.com and www.example.co.nz have the same behaviour as well)