i a b c [right arrow] d e f

results in vi displaying the text:

ab

Note that the key f generates a bell as vi is no longer in insert/append mode.

If you're seeing different behavior I can only assume you've got wildly different terminal settings, you've configured vi and forgot about it, or have aliased vi to vim or some vi variant from ports.

Either way that lends credence to the idea that judging someone for being uncomfortable at a vi prompt is a bad way to interview candidates.