Microfiber (normal) inserts should be placed in a pocket diaper, never against the skin, as it is so absorbent that prolonged contact with this material can irritate or burn the skin.
Some microfiber inserts are covered with a dry-acting fabric such as Coolmax, micropolar and can therefore be placed directly on the skin without risk.
The microfiber is easy to recognize, thanks to its lined/curly appearance, it is the fabric of household flaps.
Microfiber is cheap, absorbs quickly, but can cause compression leaks. It is a good idea to pair the microfiber with a natural insert such as cotton or hemp. When materials are over placed, the microfiber is applied to benefit from its absorption speed.
Microfiber is a synthetic fabric. When we talk about pollution, we first think of plastic bags and bottles that are thrown away carelessly. But synthetic clothing is also part of the problem. When our clothes are washed, broken plastic fibres enter the waste water and cannot be effectively filtered with washing machines or sewage treatment plants. If all households are added together in this way, there is enormous pollution. (This paragraph is taken from this page: http://guppyfriend.com/testseite/anwendung-und-eigenschaften/francais this solution exists to wash clothes, but is unfortunately not suitable for cloth diapers).
It's a pretty young consciousness from my side. I used microfiber inserts for most of the time I used cloth diapers with my children. I wish I knew these details at the beginning of my cloth diaper adventure. I probably would have made other decisions.
Having said that, I remain convinced that the use of cloth diapers, even with microfiber inserts, including industrial laundry detergent, remains more environmentally friendly than the use of disposable diapers.