The "worst" example? I don't think I turned in a ranking. You asked for concrete examples of a problem. It is one. It's part of an unknown but decidedly non-zero number of examples where the www subdomain meaningfully differentiates hosts in the real world, where we live.
If there's a specific reason this example or others aren't worth considering, that's a bit of goalpost motion, but a more clearly articulated case can be worth it.
> my comments are restricted to the "www" prefix.
I'm glad your comments are. The change under discussion does not appear to be. Per comment #16 under the ticket:
"the domain m.tumblr.com is shown as tumblr.com."
Apparently the policy of identifying some subdomains as "trivial" is not limited to www.
Sortof raises the question -- once a player like Google decides it can designate a subdomain as trivial over its common (but not universal!) redunancy, what keeps them from stopping with www?
> It only concerns the entirely redundant "www"
Commonly redundant is critically distinct from universally redundant.
And allowing domain holders the possibility of treating them as redundant is a distinct situation from unilaterally imposing it.
> How will they know the floor wasn't accidentally omitted instead?
This is nonsensical. This www change does not hide subdomains that meaningfully differentiate among "floors". It only concerns the entirely redundant "www" ("'1st floor' for a one story building"). Accidental omission of "www" a total non-issue... in the real world, where we live.