The shady company 25.io (https://twitter.com/25io), apparently based in Tianjin, China, initiated an Indiegogo campaign for their Mou Markdown editor back in late 2014. They received $27,334 of the $20,000 they requested, promising to ship version 1.0 of Mou by April 2015.
The only updates they’ve posted since the end of the Indigogo campaign were to briefly mention that they were “ashamed” for not having delivered 1.0 on 31 August 2015 — almost six months ago.
So, avoid Mou as a Markdown editor. In beta, the project was sub-standard, anyway, freezing on saves — often.
Backers of the project on Indiegogo have suggested https://www.typora.io/ and https://github.com/dvcrn/markright as alternatives to Mou.