A lot of bugs go through from patch to patch, some are game breaking, some not so much. Some even go seasons without being fixed. The only thing I think reporting bugs does is help Riot catch any big impact bugs. Everything else seems to have no rhyme or reason to why or when it gets fixed.
So, what I want to do is to make a place that is constantly updating as to what bugs are live, how long they've been live, and what are the replications for the bugs. (Well, maybe not me, kinda hoping to pawn this idea onto someone more motivated). If it got enough community support I think it would have a real impact on what bugs are dealt with.
Some bugs off the top of my head (may not be exact on some things, but it's a start):
* Matchmaking: If two people have the same role as desired in any of their two slots and neither of them gets it, they will get the role the other had chosen but didn't get (speculation on trigger conditions). Possible it might be limited to parties (only way I can document it). Appeared in Patch 9.10 (might have been 9.11 though).
* Warwick: Q when tapped will sometimes swing you behind the enemy as if holding it down. Possible it might have to do with high movement speed and not coming at them straight (best guess off of memory). Appeared with rework.
* Warwick: W will not always give movement speeds for blood trails. Directional movement speed sometimes is off by a noticeable degree. Actual blood trails and visuals do not always line up. Delays to blood trails appearing and disappearing. Appeared with rework.
* Warwick: Passive multiplier is actually 2.5x, not 3x. Assumed to have appeared with rework.
* Sivir: Ricochets after the first hit do not proc Dark Harvest. Possible problem with the on-hit damage on her W and the way that's coded (speculation). Noticed in 9.11.
Feel free to add any others you can think of in the comments below, especially ones that have been around for a few patches.
**You** can prevent another Mordekaiser