[Foxlit]

There is no way to check whether two units are actually the same unit with secure code, including macro conditionals. More specifically, you cannot choose which spell to cast based on whether your target's target is you or some other friendly player.

Originally Posted by Haleth Deleted my previous post because it's wrong. What Dridzt says is mostly correct, except 'player' should be 'self'. http://www.wowwiki.com/MACRO_cast

The Wowwiki page is blatantly wrong as far as "self" is concerned. You're also falling into the trap of thinking that target= implies unit comparison, rather than simply setting which unit the conditional operates on. [On a tangent, that's a slight benefit of the @unit syntax: it's more difficult to misread in this way.]

WoWWiki UI articles are generally not actively updated since the WoWWiki/Wowpedia split. In this case, the relevant wowpedia page is http://www.wowpedia.org/MACRO_cast , which removes some of the inaccuracies and subtleties that confused you so. Please consider linking to Wowpedia rather than WoWWiki in the future.