When you get an achievement in FTL, the description notes which difficulty you unlocked it on, Easy or Normal.
What happens if you have an achievement on Easy, then manage the same feat again on Normal? Do you get the achievement again? Is the achievement “upgraded” from Easy to Normal?
If you have it on Normal, can you get it on Easy and have it downgraded?
I got the “Asphyxation” Achievement twice, once on easy and later on normal.
I don’t know about downgrading but you can definitely get achievements twice if you get them the first time on easy and they then get upgraded to normal.
The achievement only shows normal difficulty unlock for upgraded achievements.