You make a good point. The specifics of the honor system are hidden, so none of us know the actual mechanics.
The honor faq https://support.riotgames.com/hc/en-us/articles/115008474148 repeats the phrase 'clean games' multiple times. To me, that insinuates that if you're reported in a game, any negative behavior will negatively impact your honor growth.
So, I try to avoid everything that can be caught by the IFS.
Don't call for ff, pressure people to vote for ff, or give reasons that we should ff: that's giving up/demoralizing. Just initiate the vote.
Don't argue. Just mute.
Don't insult. Just mute and report.
Don't point out people's KDA or cs unless you're very specifically praising them.
Don't say GGEZ.
Don't say gg after someone's mistake.
Don't open mid, threaten to open mid, or joke about opening mid.
Don't afk, threaten to afk, or joke about afking.
Don't intentionally feed, threaten to feed, or joke about feeding.
Don't call people trolls or feeders. Just report them.
Don't ask for reports. Just report them yourself.
Don't say you're muting people. Just mute them
Don't say you're reporting people. Just report them.