Like PalmDOC, the Mobipocket file format is that of a standard Palm Database Format file. The header of that format includes the name of the database (usually the book title and sometimes a portion of the authors name) which is up to 31 bytes of data.
The first record in the Palm Database Format gives more information about the Mobipocket file. The first 16 bytes are almost identical to the first sixteen bytes of a PalmDOC format file.
The compression bytes are the first two bytes in the first record
of the Palm Database Format not
the first two bytes of the file.
The details for the Palm Database Format can be found in the Palm Database Format wiki
That info isn't duplicated in the MOBI wiki because it's the same.
While I was typing away trying to explain it... you figured out yourself.