The mod seems to override high mipmap settings, forcing them down to a lower level despite being set to high by the client. This causes unavoidable graininess for distant blocks.

The only thing I know of that could be a cause of this would be irregularly-sized textures (as in, not a multiple of 16) for any blocks or items added by the mod, but I've been told that there are no such textures in the mod, so I'm not quite sure what else could be causing mipmap levels to be overridden.

I've ran the mod with absolutely nothing else installed (no other mods or resource packs), and the mipmap issue persists.

Some comparison pictures:

A superflat world without the mod installed, with maximum mipmap settings.

A superflat world with the mod installed, also with maximum mipmap settings. Note how much rougher the grass looks from a distance.

Forge version: 28.1.115
Mod version: 1.4.7

Actually, I found this error in my logs:

[19Jan2020 23:53:39.820] [Server-Worker-3/WARN] [net.minecraft.client.renderer.texture.AtlasTexture/]: Texture upgrade_aquatic:block/bedroll_particles_yellow with size 16x15 limits mip level from 4 to 0 [19Jan2020 23:53:39.822] [Server-Worker-3/WARN] [net.minecraft.client.renderer.texture.AtlasTexture/]: textures: dropping miplevel from 4 to 0, because of minimum power of two: 1

Presumably this is the cause?