Although I’m currently not done surveying the silver league (only one tier done ! 
), there was two testimonies interesting enough to be mentioned in this thread :
The first one is about the consequences of smurfing on unexperienced players :
This confirms what I supposed about the consequences of smurfing on less experience players : frustration, and for some, a deterrent to even play the game.
That’s why I think smurfing in those leagues slowly kills the game, and why it’d be important for the devs to realize it.
The second, on the contrary, relates to what leads to match-up smurfing :
The interesting part is that it’s a perfect example of what leads some users to become match-up smurfs : despite allegedly not complaining about balance anymore, freelosing entirely one match-up in fact relates to the intimate conviction those match-ups are imbalanced. And that nothing those individuals could do or say would change that : so after complaining, then cheesing, the next step is freelosing some match-ups entirely.
There’s a fix suggested, though, the possibility to veto some match-ups on the ladder :
- I think that it wouldn’t be fair to have users playing only one or two match-up instead of three, thus discarding the less favorable ones, to be ranked in the same place than those who made the effort to overcome the more difficult ones.
- However, it might be a good idea for unranked, since unranked doesn’t ranks players, is more meant as a training ground ; and since that may allow for match-up smurfs to stop freelosing.
Match-up smurfs are minority though ; but even for training purposes that suggestion could come in handy. 
I’ll also use the occasion to underline the first post has been updated and revisited. 