I do it for my pygmies (obviously), but for my Werner's big enclosure I have several really big pots in there. It's almost solid soil. I find the soil keeps the humidity in nicely, and I've never ever had problems with mold or poop in the soil. My dirt is not covered, but she is cup fed, or sometimes eats her crickets from the leaves. She rarely goes near the bottom as it's a pretty big enclosure for her. Oh, btw, it's not glass.
I've also had sternfeldi in the same enclosure (not with the Werners), and they never went to the bottom to feed in the dirt. The crickets tend to go up, not down.
Oh, forgot. Also had a Flap Neck in a planted glass enclosure. It was planted fully and that worked well for humidity. No mold, no festering poop, no soil ingestion. I've never used substrate with pieces of bark, so *if* soil was ingested it wouldn't be more than a bit of dirt.