1. By way of fluff, common sense, probable designer intent and 6ed references, it's a pistol.
2. Under a RAW (Rules As Written) interpretation, it is not a pistol. I.e. NOWHERE in its rules does it state that it either a) follows all the rules for a regular pistol or b) ignores movement and range mods. The rules ONLY state that it, when combined with a pistol, is MSx4 (and is MSx3 by itself), and always stands and shoots.
2.5. Yes, GW Design Studio is populated with dolts and Gav Thorpe clones, who lack any basic understanding of games design or English grammar. This has been the case for years, and will only grow worse in the future.
3. My personal (and some other people's) policy for cases where two competing rules interpretations exist is to use the worse one. First, you never know if GW intended this to be the case (they've made several 7th Edition rules changes deliberately, wherein people initially thought these were "typos" and omissions), and second, this way you avoid any rules arguments whatsoever (few opponents would strenuously object to gaining such an advantage). On the marginal plus side, the champ is BS4.
4. Realistically, if someone were to use six-shooters on me, I'd let them claim that they follow all the normal rules for a pistol as well. That said, I would fully expect a 5-game tournament to feature at least one game with a player who disputes this. Again, in this case there is genuine RAW ambiguity; citing 6th Edition interpretations doesn't work, since someone who'd started to play in 7th wouldn't have known of any of them (and since rules DO change between editions). The best way to handle the problem is to discuss the issue with your opponent BEFORE the game - and if he/she/other persists in a strictly RAW interpretation, well, so be it, but then you can always tank his Sports score.
5. The "Always Stand and Shoot" logic doesn't work. By same rationale, Crimson Death, described as a "two-handed weapon" and giving the user +2 strength, should be a GW and strike last. It isn't and doesn't. Weapon-specific rules trump ANY rulebook weapon rules UNLESS specifically otherwise noted.
6. If GW ever decides to release a 7th Edition Empire FAQ, I'm 98% certain that they would rule the Repeater is a pistol (probably with something like "duh, of course it is"). Understand, these people have no clue about how the game works, and tend to play very little against those who do.