Can you explain when exactly this is a problem?

The case-insensitive comparison was derived from CommonsHelper2, which does it the same way. The assumption is that:

• It's very rare that two templates with the same name but different capitalization exist. If they do, it's either a mistake that needs to be/will be fixed, or a redirect.
• I feel we should be defensive, especially when checking for forbidden templates and categories. If a file is marked with {{nOcOMMONS}}, I feel we should still block it, even if this template transclusion is technically broken.

Also, if we make the comparisons case-sensitive, all config pages need to be updated to include all redirects.

In T232328#5479031, @thiemowmde wrote:

Can you explain when exactly this is a problem?

This will only cause a problem if article titles overlap, with differing case. I'm sure this is an extreme edge case, maybe never. Practically, it bothers me because we aren't tracking the correct title for these articles. When a redirect template isn't available, we've created a situation where the user might see configuration for Template:Nowcommons, and it will be difficult (and uncertain) to find that the correct page is Template:NowCommons.

The case-insensitive comparison was derived from CommonsHelper2, which does it the same way. The assumption is that:

• It's very rare that two templates with the same name but different capitalization exist. If they do, it's either a mistake that needs to be/will be fixed, or a redirect.

I think this is correct, except that the redirect assumption seems fragile. There is *always* a redirect from a lowercase title to the correctly-cased title?

• I feel we should be defensive, especially when checking for forbidden templates and categories. If a file is marked with {{nOcOMMONS}}, I feel we should still block it, even if this template transclusion is technically broken.

Defensive is good, and I'm okay with not making my proposed change unless we run into real scenarios where we over-zealously block an import due to templates with overlapping case, for example.

Also, if we make the comparisons case-sensitive, all config pages need to be updated to include all redirects.

No, I believe that the config pages only need to be updated to reflect the correct page title case. Redirects are transcluded as part of parsing, so the ParserOutput will include the resolved template names.

This task does feel mostly cosmetic. I was goaded into action by the thought of having to reimplement our defensive logic on the FileExporter side, it seemed like I was perpetuating a mistake.