To be fair it has both happened to me and I have done it to others for some of the simpler things when tinkering mainly just led to it being doable in a short amount of time.
For the most part nobody cared; everybody had a new hacked game to play.
This. And frankly, why would you care? Finish your own version and release it too. Worst case scenario is that we have two versions of the same game available, and if people behave like grown adults, they might even work together and say "Hey, I like what you did with that font, but I think this little menu tweak I made to improve gameplay really steps it up, wanna swap notes?" and maybe end up collaborating to create a joint effort patch that gives us the best of both worlds and has two people polishing up the translation/localization.
As much as I appreciate fan translators and hackers, I have no particular loyalty to any of them. If I want to play a game that isn't available in English and someone releases it, I don't care if they stepped on someone elses toes. I still get to play the game, and unless it's a complete hackjob compared to progress that's been shared by someone else, I'm more than happy to just enjoy what we've got. Like, I love all the stuff that AGTP has released, and the level of quality they put into it, but believe me, if someone swung into RHDN tomorrow and dropped a quality English translation of Star Ocean: Blue Sphere, I wouldn't shed one tear for Ghideon. He's already dropped multiple projects because others have beat him to the punch, and I feel like the community could take a few lessons from those situations. If you're working on something, don't take for granted that you're the only one interested in it, and if you're taking a long time because you don't have much time to devote to the project, realize that you have zero right to be upset when/if someone else outstrips you.