To Be Fair, It’s a Lovely Hat
It’s not uncommon for characters to get re-worked in updated versions of games. Even within a single game, the advent of patches makes ability tweaks so much more accessible. But a change on this scale? That’s not something you see every day.
In all seriousness, the hat actually adds quite a bit to Bastion’s design. He already had a bird friend in the first Overwatch title, which helped characterize him as more gentle than his literal-death-machine body would imply. Something as simple as a hat accomplishes the same goal. Either it’s something he found and thought “looked nice”, or it’s a gift from some other character – a gift he appreciated enough to continue wearing. In either case, the hat does a lot to humanize an otherwise-robotic exterior.
There’s also a slightly less important issue of complete ability rework, nothing special. Two abilities in particular are being completely replaced: The self-repair option was replaced with a grenade toss – this’ll stick to enemies and the ground, but can bounce around walls to find their mark. The robot’s Ultimate ability is getting a similar overhaul: no longer will he transform into a tank and roll around. Instead, he can call artillery fire onto any three parts of the map you want.
For one final change, Blizzard is changing Bastion’s role in Overwatch’s sandbox. The damage falloff and fire rate are both getting cut for his primary walking-around mode, granting him a much further effective range at the cost of lethality. And for his alternate mode, he’s no longer stuck as a rooted minigun. While slower, he can now move around the battlefield, blasting the enemy away with crazy damage.