It's more comfortable to boil it. Eating the bark will tie your stomach in knots. You'll develop this annoying sense of tightness in the gut, and a dryness in your mouth that won't go away. I wouldn't recommend taking more than a gram this way. Plus, I'm not sure how the body responds to the sand like substance like mimosa bark. I believe the typical response to insoluble fiber is that the body forms a mucous gel around fibers, which allows the fibers to be pushed more freely in the body. However, mimosa contains a lot tannic acid, which is an astringent, which has a very drying effect on mucous linings, such as mouth, and intestines. It's probably hard on the stomach to ingest bark powder along with tannic acid.
You don't have to do a chemical extraction in order to enjoy the benefits of the medicine provided by mimosa. You can just boil it and drink it. It will taste bad, but it's very good medicine. In fact, many people enjoy the full range of alkaloids that mimosa tea provides, that typical naphtha extractions do not preserve.