Ever since the snapshot that first introduced a new way for texture packs to work (Where they are stitched together in game), there have been constant white flickering lines or gaps between every single block. Not just blocks, but the actual creases in them. The individual parts of stairs produce this effect, and torches give off weird thing sticking out lines sometimes.

It's incredibly distracting, because this sub-pixel gaps flicker and move as you walk around.

Let me know if you need any other examples (Such as a video)