It's NOT a reson for LPQ
Pretty often in the beginning of ARAM game I wait on recall for extra gold, obviously, to buy start items set that I can't afford with initial 1375 gold - B.F. Sword + boots (1550 + 325 = 1875 gold) or Tear + Catalyst (750 + 1200 = 1950) + sometimes up to 140 gold for health/mana potions. And when I forget to do something like running on the spot or back and forth on the platform, and just standing still (watching gold counter) I get warning message - "You should become active or you gonna be punished blah-blah-blah", I press ok, move champ a couple steps left-right, buy my items when I have enough gold, join my team, we win the game, I play another one and one more... and suddenly find myself in LPQ.
Only AFK-related events during given period were whose warnings I was getting in the beginning of my games. More than, I was only getting first warning, "You should become active or...", I never kept standing with no action after that one, so I wasn't getting 2nd message which is smth like "because of your inactivity the game will now exit". So I guess, thay are the reason for 5 LPQ games punishment... I got it 3 or 4 times for that reason, now I'm always running in microcircles on the platform in the beginning of my ARAMs so your stupid LeaverBuster knows I'm not AFK, butI fracking anyways, isn't it retarded - there was only 1st arning, my team WON over a half of those games, my teammates never reported me for AFK, but that shit still throws me in the Low Priority Queue. Frucking amazing...