I know this problem has been presented many times before, but I don't understand how my graphic-settings (reading from https://mojang.atlassian.net/browse/MC-2514) can be blamed if I want anti-aliasing in my game and it suddenly shows pink lines whatever I do, while this doesn't happen to any other game I know.
I'm currently using a Sapphire Radeon HD 6870 with the latest drivers available. Some Nvidia users fixed this issue somehow, but most Radeon owners are not able to fix this in any way.
Example, taken from an issue that presented the same problem, is shown below.
I think a fix would be to allow in-game anti-aliasing, or just to fix the origin of this problem.
Gathering information from here and there, I heard the Watershader mod seemed to fix this in the past: http://www.minecraftforum.net/topic/727846-anti-aliasing-in-mc/ (last post)
Here more people with the same issue from a more recent thread http://www.minecraftforum.net/topic/964617-looks-horrible-pink-lines-between-blocks/
It still persists nowadays, I think it should be fixed within Minecraft itself, the only way to fix it atm is to either use mods or turn anti-aliasing off :\