There is chaining in-game - it's for fishing Brilliant Aura pokémon (tried and confirmed it myself). With the amount of people here I've seen hunting since launch, if there was a chaining mechanic, either the dataminers or the hunters in general would have narrowed it down at this stage.
That other post was me too, it's not just me who's said this though. Since launch and the start of the shiny hunt generals, there's been loads of people complaining about the chain failing. Full disclosure, I was a fat handed idiot and closed the game w/o saving, lost my initial shiny sheep (had a sociable mark, I was raging), ended up finding another after rebuilding my chain from 252 to 500 and beyond. I feel even with SM's chain building, shinies were more common for me between 10 and 31 (or last stop before max odds, whatever that was, it was 70, granted in SM as opposed to USM) than chain shines are for people with supposed max chance.