Could a really, really, really fluent speaker of Old English, or maybe Klingon, or Esperanto or Volapük, affect an authentic accent? As in: an accent when speaking English?
If so, I would give a lot to hear a recording of the elicitation paragraph read by one of those folks who wouldn’t normally be expected to appear on the list.
I would think so — at least, a fluent speaker who knew basic linguistics could. Do the stress patterns of your other language, replace some of the sounds English has and your language doesn’t with other sounds. Old English would involve, say, making all fs vs between two vowels, and the reverse anywhere else . . . mostly we can do accents because we know them, but I don’t see why we can’t figure them out, too.