The problem is likely to be that you are attempting to turn outline defined fonts, i.e svg, ttf, or PS, into toolpaths/gerber plotter outputs for placement on your layout, with the associated problem of loops/holes within glyphs.
What you ideally need for these applications are centreline defined, a.k.a. engraving, fonts.
The FootprintTextForPCB utility mentioned above uses the centreline defined Hershey engraving fonts for this reason.
If you are using Inkscape already, I believe there is the ability to install the Eggbot Hershey fonts for such uses, which can then be exported as gcode or paths. There is also the Inkscape2pcb export script on github which can export a gEDA PCB format footprint from Inkscape that Kicad can easily import, which is an alternative to svg2mod that uses Inkscape's own internals to converts paths to segments, but ignores polygons, unlike svg2mod.
There are lots of ways to skin this particular cat, but a centreline defined font is probably the most important aspect if converting to line elements.