Alvoria

Still around in 1.8.

It's also worth nothing that having Minecraft open in a non-full-screen window and manually adjusting the width of the window also causes this. It doesn't have to be because of your monitor, just the proportions of the window Minecraft is running in.

@Kumasasa: Because it looks nice? I don't see what you're getting at.

Some resource pack artists may want to use a resolution that falls in-between the standard resolutions, and Minecraft's mipmapping feature has a problem with that currently. No self-respecting resource pack creator wants to tell people not to use their pack because of a rendering issue. A lot of us were psyched about the new RP format because it would allow us to do things like this.

To put it another way: if all texture resolutions are going to be supported by Minecraft, then all texture resolutions need to be supported by Minecraft. It's really that simple, at least to me.