I'm brand-new to Inkscape and vector drawing in general, and I'm trying to start with a letter, and it seems I'm already running into trouble. For some reason, the top portion of my letter - R, in this case, in the font Celtic Knots - is not visible. Occasionally I can click around and do a dance and say the magic four-letter words, and the top portion will come up. Then I go to modify my letter, to erase a part of it, and absolutely nothing happens. Nothing is erased.

Running Inkscape on a Mac, OS X 10.11.5, newest version of Inkscape and XQuartz (just downloaded in the past few days).

Here's a screenshot of my weird letter issue (the red rectangles are not part of my Inkscape image, they've been added to the screenshot to highlight the letter problem):

I note that you are on a Mac and I am not, but try increasing the line spacing which inkscape reads as zero in some free fonts... Caps then get cut off even when there is not a line above