Which version of Unity are you using?
Does it break anything, or do things seem to work anyway?

Hm, alright. What about my first two questions?

Hurgh, what a mess. So that line fixes it in some cases, and breaks it in others. The question is in which cases does it break?
I think some depth rendering stuff is reading alpha from whichever texture property you have called MainTex, and applying that as an alpha clip, with a cutoff set to 0.5 now, by default. Are you clipping with the alpha channel of a MainTex texture?
Also, is depth blending set to Alpha blended or Off? (Should be off)

Are you using deferred or forward rendering? (Check both the camera and the player settings)

It should fade if you set it to additive

Or not use alpha at all, and do additive blending instead

Is alpha blending still enabled? Try alpha clip instead, and turn off alpha blending

You don't want Alpha blending and depth buffer writing at the same time, use alpha clip instead of alpha in that case

Oh, wait, why are you enabling writing to the depth buffer? I'm almost certain that's the issue