The difference between a Riven Main and a "Riven Main"

A Riven main to start is a person who enjoys playing Riven. They like the character, kit, challenge, etc. As such they study guides and streamers and practice in solo games. While they may not be good they understand Riven. What makes her strong, weak, which matchups she wins and loses. Now, some of these people may be Toxic like any other player. But are not especially toxic and often less likely to flame team mates, as to them it is very obvious when they fuck up because it didn't look like what Boxbox does.

Then there are "Riven Mains". These are players who since S2 have assumed Riven is the most broken, uncounterable, powerful and freelo champion in the game. Often they even assume she is easy to play. They only play her either when she is specifically strong or assuming she is always strong. Then when they lose an unfavorable matchup, die, screw up a combo or team fight, or just are beaten by better players. They cannot fathom that Riven is not OP, easy freelo like the gameplay boards have told them for 6 years. So they assume somebody else must be at fault. And flame the nearest team mate, programmer or matchmaking system near them.

Now this applies to most champions. But to Riven especially given her reputation and popularity. And of course real Riven mains can be toxic and "Riven mains" can be polite. The main factor is if they are playing Riven under the assumption that she is freelo. Or playing Riven because they like Riven. The rest is just the average results of those mindsets.