It’s a common question and I think it all comes down to the visual outcomes.
Simply egg shells are great in both composts and worm farms. The reason you might have heard not to put it in your compost is that it will probably still look exactly the same when you go to harvest your compost – some people might not want to see egg shells in their soil. This doesn’t make it bad it just mean that for the egg shell to be broken down naturally it can take a few years. It’s actually great to add egg shells due to the high amount of nutrients including calcium(two fifths by weight), magnesium and a few others.
We prefer to dry them in the sun and then blend them to a fine powder. This allows you to sprinkle the powder around the garden and help reintroduce nutrients back into the soil a little quicker.