Assertion: 'For the purposes of applying the bidirectional algorithm to the paragraph-level container that a bdi element finds itself within, the bdi element must be treated like a U+FFFC OBJECT REPLACEMENT CHARACTER.' Thus, when a BDIs contains text of the same strong direction as another BDI following it, the two must not form a directional run as would be the case if the BDIs were just SPANs, even if the two BDIs are not separated by anything at all.