We all have ignored someone, then later grouped with them again achieving the same undesirable game play.

Some people would like to see an addition to the ignore button, call it what you will, but while they have this special ignore will be barred from future games with you.

Think something like this would be a nice feature to have then having to bail costing you time and stats.

I've never been grouped up with someone I ignored, and I can only recall a couple times where I ended up in the same game as someone from a previous game. IF this is actually happening to you though, you raise a valid point. I assumed it was already the case of matchmaking wouldn't put you and an ignored player in the same game.

This feature has previously been requested and rejected for mathematical/technical reasons. The short version is that matchmaking wouldn't just be checking your list, but ten full blacklists; any positives mean that entire match has to be rejected. The simple explanation is that implementing such a solution is not easily solvable.

If you are so inclined, the problem boils down to what is known as a P=NP Problem, and mathematicians have been trying to solve that for decades. Until they do, matchmaking blacklists of this sort in any game (not just League of Legends) are not technologically feasible.