As the title says, we should be able to continue past level 30 but mastery points remain still at 30 regardless of level. Would seem cool to see what level you reach throughout your career in LoL.

Not a horrible idea but why would you want to level past 30 if you don't receive any benefits after 30? If you want a number to show off how much you've played you do have your # of wins.

As mentioned, there's the win count; it doesn't really reflect your skill so much as how long you've been playing, since even for a very-high-elo player it will only average out into the 55-60% range or so.

Having a level cap at 30 does help, though; it's high enough that it's not quickly reached, but low enough that anyone seriously playing over time WILL reach it readily, so it serves as a good, easily-recognizable mark of a long-time, serious player.

Though it might be interesting to see if you could look at how much XP you've accumulated past the level 30 mark. (which is about 40,000 XP from level 1)