Yeah that would be super flexible, but would also raise the bar to using those blocks. We certainly wouldn't use "≡" which doesn't mean anything to Snap! users; it'd have to be "identical," making the block even wider than your version. And it'd make debugging harder; you'd get an error message in a custom block because of the wrong choice of equality test in a sub-sub-subprocedure of the one where the error manifests itself.
I hear you about a global setting being too broad, but I think a per-block setting is too narrow, especially if there's an explicit Boolean to set it. Maybe something more like how compiled HOFs work, with an option in the context menu and then a symbol in the block. (In that context, where the setting is visible but not directly settable, a big bold ≡ might make sense.) (The forum isn't cooperating with my efforts to change the font of a character.)