Okay, it’s disabled on Firefox as well. Though one caveat. When I click the heart next to Create Community, it does provide a popup: This page is asking you to confirm that you want to leave — information you’ve entered may not be saved.
I’m expecting that popup for any of the navigation links with text entered (or really any reason as to why the link isn’t working when it normally does). The lack of that message makes it work ‘other than expected’.

And on Edge, same behavior. (All these are on desktop Win10 environment). “Navigation Bar Disabled while text in comment field” would be a fitting description.