the intention was probably for this to match something a bit more restrictive (e.g., matching ^/wiki(/.*)?$)

I'm looking at the diff where the RewriteRule was introduced, and I'm pretty sure this is right -- it's replacing a

ProxyPass       /wiki                fcgi://127.0.0.1:9000<%= @docroot %>/w/index.php retry=0

so we went from a path argument to a regex. But some history from @Joe would help to confirm. And we'd still need to make sure nothing else has started relying on this in the last five years.

In T357595#9544806, @RLazarus wrote:

the intention was probably for this to match something a bit more restrictive (e.g., matching ^/wiki(/.*)?$)

I'm looking at the diff where the RewriteRule was introduced, and I'm pretty sure this is right -- it's replacing a

ProxyPass       /wiki                fcgi://127.0.0.1:9000<%= @docroot %>/w/index.php retry=0

so we went from a path argument to a regex. But some history from @Joe would help to confirm. And we'd still need to make sure nothing else has started relying on this in the last five years.

If you go back further in history, you'll find we used to use an Alias directive, which of course behaves slightly differently too.

As for your question: I don't think anything relies on this, or if something does, we should be ok breaking it.

Change 1007026 had a related patch set uploaded (by RLazarus; author: RLazarus):

[operations/puppet@production] mediawiki: Restrict /wiki RewriteRule

https://gerrit.wikimedia.org/r/1007026