Is it possible to get punished simply from being reported even if you do nothing wrong?
No. If you break no rules, you don't get punished; I have seen maybe one or two edge cases where such happens, but they're inconceivably rare, and consequently negligible for anyone who follows the rules.
I've been chat restricted before without even using curse words, just talking back to 3 toxic premades saying stuff like "stop flaming and play" "quit spamming pings" "you're being immature"...
Calling people immature does constitute insults, and you could've very well been punished for continuing a detrimental argument besides. I can't say for certain without seeing the aforementioned logs, but it's not uncommon for continuous, slight misbehavior such as that to eventually warrant a punishment.
Ever since then, I've decided to turn team & /all chat off, most of the time people chat in game is to be toxic anyways, but is that enough to be safe from premade children who tell each other to report their team when they're losing?
If you don't say anything in chat (which is what I'm assuming, just taking the next logical jump from turning team/all chat off), you won't get punished; because, if you're not chatting, that by extension also means that there's no chance you're participating in chat misbehavior, so their reports will mean nothing.
And, win or lose, reports do the same thing; they trigger the IFS to review the reported player. If that review comes back with no misbehavior, the IFS will simply discard the report(s).
