Obviously it adds a ridiculously large amount of artifacts when it is enabled, but 4x the resource cost is quite a lot. Do 99% of games exclude it, or am I just using it incorrectly?
I would guess that practically all games use it, the artifacts are mostly unnoticeable on textured surfaces.
Yeah, but what about plain materials without textures? All games have those, and they don’t look like this.
I really don’t think that is true. But regardless, not all games use baked lighting or UE4. Adding detail in general and paying careful attention to lighting are useful tools for achieving a good result.
These are some screenshots of my test scene with lightmap compression enabled, using only flat uniform surfaces with no textures:
I consider an acceptable result personally.
Ultimately though the choice is yours, if you feel that turning off the compression is worth a 4x memory/disk cost then do it. It’s not really all that important what other people are doing if the result is unacceptable to you.