Externally, I agree. On a side note, my company will not provide references when you leave and forbids managers from providing any references.

At my company, internal postings notify your manager when you apply, so there's no avoiding it. It's generally better to talk to them first so they aren't blindsided by the posting. Otherwise, if you don't get the new position that could create some friction with the existing one. My company can also trap you in your current position if they designate you as a "key resource".