If you buy peat that has not been milled to a flour. Home Depot carries Sunshine, this brand of peat still has chunks. It is not ground to a flour consistency. Sifted peat, where you throw out the fine particles, can be a good component of your bonsai mix.
Exercise care when using peat. One issue with a mix that is dominated by peat, when it dries out it will shrink. When rewet, it does not expand. A mix with too high a percentage of peat will over repeated cycles of going from wet to dry, will shrink to a compact "brick" of soil. This will loose air voids, and create zones of no oxygen for the roots. Dry peat is difficult to rewet.
However, if you are careful to avoid letting a peat based mix getting too dry between watering, you can use peat very successfully.
A pumice-akadama mix is the "proven go to" for the Japanese and many Americans. But if you look at trees in major USA & Canada Bonsai Shows, some very fine trees have been grown in a wide array of different potting media. Not everyone uses Akadama.
IF you understand how to water a given mix, you can grow bonsai in just about any media. But understanding and perfecting watering and fertilizing techniques is not a trivial problem.