FMs outside of 88-92 can be designated noncommercial. Can that not be done on the AM dial?
Not that I am aware of. If so that would be a good thing especially for these type of stations.
Some of the heritage educational stations operated by universities carry a something of a NCE designation. I don't know what significance that has at the FCC level. I think they can be converted from NCE to commercial without a lot of hassle. In today's world any FM granted a spot on the dial in the 92.1 to 107.9 spectrum as an NCE cannot be converted to commercial by the licensee or as a part of a license sale/transfer. The channel if abandoned by the not-for-profit licensee then becomes available through the AUCTION process.
However, some early college owned not-for-profit stations were not given NCE preference or station when they were granted and have been converted and sold. (I'm thinking of WAJC, Butler University, in Indianapolis if my memory is not playing tricks on me.
AM NCEs I am thinking of would include WBAA at Purdue, WILL in Champaign-Urbana, IL and WHA in Madison, WI. In the area of religious programming AM's non-commercial would be the original WMBI at Moody in Chicago and KFUO owned by the Lutherans in St. Louis.