Ah-HA!!
I installed, and I have the exact same problem!
After your last comments, I was going to say that if this is only happening in this 1 font, it may be that the font is just not very well made. Inkscape seems to be quite particular about fonts, and if a font isn't well made, sometimes Inkscape can't use it at all. But since I installed, and having the same problem on Windows, I think this is just something about how the font is made. It seems like there is some unseen border, and the font designer made the letters too big for that border.
However, as soon as I convert the text to path, the entire letters are showing up! So as long as you can handle the paths, that will probably solve the problem. Let me find a good tutorial, to help you learn about path editing, to remove the portions that you don't want (actually it's usually referred to as node editing)....
This one, in the manual, is meant to introduce to paths:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/AShortExampleLogo.html And the middle part of Help menu > Tutorials > Advanced is also an introduction to paths (just ignore that fact it's called "advanced" - it's meant for teaching newbies). Right below the section on pasting, starts the path info.
Wow, just realizing for the I-don't-know-how-many times, that we need a nice and newer tutorial, for teaching node editing and path manipulations. Gotta put it on my list
But for now you can visit the Home tab, and find loads and loads of tutorials. The way I have them organized, generally how I decide if a tutorial should be for beginners or intermediate, is which features are involved. If a tutorial uses a lot of node editing or path manipulations, it's usually in the Intermediate box. If it's mostly about shapes, or if it's described very, very clearly, it goes in Beginner. (Those of Mark Crutch (aka "Xav") are excellent, but they aren't set up to be searchable. So it's hard to identify which ones are for node editing and path manipulations, except by looking through, one PDF at a time.)
One thing I notice about the font, and maybe it was on purpose, but it looks like the letters are entirely hand made. I mean the parts that should be completely straight, aren't, and the curves aren't smooth, etc. I would love to see this font made with more precision. But I know that most celtic knot images and drawings also look hand made. So maybe it was just a style choice for the designer.
Anyway, let us know if you need any help with path or node editing