Is there a comment character for foreman's .env file?

FWIW, '#' appears to work as a comment character.

It at least has the effect of removing unwanted environment declarations. It might be declaring others starting with a #, but... it still works.

EG

DATABASE_URL=postgres://mgregory:@localhost/mgregory
#DATABASE_URL=mysql://root:secret@localhost:3306/cm_central

results in postgres being used by django when started by foreman with this .env file, which is what I wanted.

I THINK the app will ONLY look for specific variables inside .env, anything other than the predefined variables (pre-defined in the app files) will be ignored.

So anything you write there that is not used in your application files you can consider a comment. Similarly if you wanna comment out a variable then basically any change you make to the name will "comment it out"; for example, if you change DB_HOST to #DB_HOST then the latter will be ignored because the application is looking for 'DB_HOST' not '#DB_HOST'.