IE11 displays line breaks as missing gylph (�)
I minified a font with fontmin. I used this demo repro.
The Demo can be found here: https://jsfiddle.net/nvtwsoo4/2/
Internet Explorer 11 thinks, there is no SPACE character in the font, so it displays a missing glyph character at every line break (<br />):

possibly related to #39
possibly related to #39
I would say that they are exactly the same bug.
I thought this was strange as well. If you pass trim: false in the opts it will include the space. The downside is that for certain fonts it is replacing the space with some other glyph. This leads to another bug. See #43
Same issue here. I did try patching fontmin using https://github.com/ecomfe/fontmin/pull/45, same problem. I suspect a problem in fonteditor-core (see https://github.com/kekee000/fonteditor-core/issues/7 created by @grumpy )
context : using fontmin to subset the roboto webfont family for 15 countries.
It unnerving, because aside of IE11/Edge, my fontmin-based scripts works great (IE8 don't have the bug, btw).
Too bad, I think I'll try https://github.com/filamentgroup/glyphhanger for my need, but I would have prefered to have only JS as dependency (glyphhanger uses JS and Python)