LÖVE

In certain circumstances Quads leak surrounding color from their texture atlas, such as drawing at floating point coordinates or using FSAA.

This leaking shouldn't be patched by every love2d project separately but rather in love2d itself.

Also I'm ignorant of inner workings of love2d and would like to know whether this is doable without significant code changes.

The "leaking" is intentional, that's how OpenGL works.

LÖVE would have to introduce a new drawable object that takes images and then pads them just like the lovers have to do now. That requires some new code, but not a huge amount. I guess the hardest problem is implementing the proper texture packing algorithm.