Hi, i'm "level 54" lol. I have NEVER used any cheat engines or glitches to level (besides that Esquago thing that happens every now and then where the enemy ships don't shoot back...). I actually hit level 51 on accident. It surprised the heck out of me when it happened. I was killing vets at kingshead working on the enemies defeated leaderboard and BAM i glowed! It is a glitch, kinda sorta... but it's not a hack or a cheat. I reported it to Disney, and i'm sure they are working hard to fix it... here's how it works....
After you hit level 50, when you defeat enemies, Notoriety points no longer show up, because 50 is "the max." BUT some rep DOES count, it just doesn't show up. Here's what i know so far:
1. the 25 notoriety that you get from enemies that give you valuables (like chess pieces or navy decorations) still counts. So if you defeated a few thousand enemies a day (like me

) you can level at a pretty quick rate.
2. the rep from invasions still counts! this is the fastest way to get rep after 50. It's how i've done A LOT of my leveling.
That's what i have so far. I hope that was helpful

(sorry for the long-windedness of my response)
Fair winds!