allow players who are playing characters aligned with the "Alliance" faction to chat or otherwise communicate directly with players who are playing characters aligned with the "Horde" faction, or vice versa;
It's all in the interpretation (as with most rules), I believe the rule is actually stating you can not be logged into one faction and talking to a member of the opposite faction through that character.

playing characters aligned with the "Alliance" faction to chat or otherwise communicate directly with players who are playing characters aligned with the "Horde" faction,
If you are playing alliance and log into a horde character you are not chatting or communicating directly from an alliance aligned character to talk to horde players. You are in fact talking from a horde character to a horde character, the rule is to stop people creating addons / hacks to allow you to talk from an alliance character directly to a horde character.

Pre-TBC many of my friends and I played both horde and alliance on the same server, in TBC our alliance guild actually rerolled to horde (transferring to a new server) with a horde guild and we merged to form a new guild. We never had any problems with the cross faction communication etc and had spoken to GM's about it many times.