The in-client reform card is actually pretty shit. It doesn't even highlight the negative phrases. Basically, it records everything you ever said and tells you to figure out why Riot wants to ban you.
This, I can somewhat agree with. I personally think it'd be nice for the IFS to italicize the lines that it found to be below the line of expected behavior, so as to better clarify to players where they crossed it.
All-told, though, discerning where you crossed the line and learning from it is a skill that's worth developing, so I can also see a valid reason for it to remain as-is.
Riot doesn't take into account "who started it". I guess it is to reduce spam. I think it could be so useful at catching negativity though.
They don't need to take into account "who started it", just "who participated". If player A starts a flamewar, and player B jumps into it, and both are reported, then both get punished.
Just because someone else started the fighting doesn't mean you get a free pass to participate in it.
That aside, if you're having trouble understanding the reason behind your punishment, you're free to post the chat log(s) provided in your reform card here for peer review. The regulars here (myself included) are pretty good at figuring out where the chat goes wrong.