I noticed how player level was linked to the level of the highest level pet you leveled up yourself. Therefore, a pet with a higher level obtained through trade would not immidiately bump up your player level. Why this is important is that you CAN'T command pets over your own player level, to avoid using high level pets too early in game.

HOWEVER...

I got a Level 57 Pet through trade and leveled it using missions. After leveling it immidiately bumped up my player level up to level 58. Now the main quests are a fluke, because I can just use any high level pet I get my hands on. It isn't a big issue now, since the level cap is still at 60, because the world isn't that big yet. But I can imagine this being a huge problem in the future, as new players will be able to get to end game content way too soon.

Yep. This has been a cheap trick (whether on purpose or accidental) for an extremely long time. Unfortunately, most of the systems in place that relate to pet levels and whatnot are not flexible enough for me to easily implement a better system. Basically, if I fixed A, it'd break B, C, and D. And so forth.

So it's just always been something that's just been in the game and most likely will remain until Sylestia is revamped.

Thank you though for reporting it. =)

Ah yes, legacy problems...
Thanks for the quick response!