The latest version of Keemei supports the new Metadata file format included in the QIIME 2 2018.2 release, and the reported bug has been fixed.
Note: if you have Keemei installed already, you’ll automatically be updated to the latest version.
There are a number of other changes to QIIME 2 Metadata in the 2018.2 release. See this forum announcement for details on what changed, as well as the updated Metadata tutorial. 