I have finished a bmf2bdf converter:
Features
- Convert .bmf to .bdf
- Converts DOS codepage to Unicode (-u option)
- Convert monospaced proportional font back to none-monospaced font (-p)
- Optional glyph spacing with -x
- Optional baseline adjustment with -y
- Brightness threshold with -l for multicolor fonts
- Generated BDF can be modified with gbdfed and FontForge
URL: https://github.com/olikraus/u8g2/tree/master/tools/font/bmf2bdf
The converter is a single .c file without other dependencies. Windows exe is included in the above folder.

Let me add some generic notes from my tests with the bmf2bdf converter:
1) Some fonts are marked as monospaced, but are actually proportional fonts.
2) The baseline seems to be shifted for some fonts (ok, it depends on the definition of baseline). But the problem is: The above bdf converter can't fix this: If the uppercase A is not placed on the baseline, then this is also not the case for the generated BDF.

Again, thanks for the effort and improvements for the filter.

I think Oliver makes good points. I also think it'd be great to be able to filter by number of characters in the font. Say I put in 64, it should show only fonts with 64 characters or more. Right now there's no good way to find more complete fonts.

I've found three Font Collections by Exile and will be adding font converted from pictures in those collections.
Unless there's any note in the picture, there's no telling about the name of the font or its author, so I guess I will have to set some name and maybe later, upon knowing more, renaming each.

Right now we've got 3,081 proportional and 3,081 monospace fonts in store.

I added few fonts from another source that I had found on the Internet - Dwarf Fortress Wiki (I added the site to the ?page=support page). Some more fonts from there will come. To my wonder, I still keep finding these resources.