We just started using On this past August and our faculty are also having a hard time reading the comments as they type them because the font is ridiculously small.  BB really does need to allow us the ability to increase the font size for comments.  Another alternative to copying/pasting from Word is if you are using Google Chrome - Click the three vertical dot buttons under the X to close, in the upper right-hand corner - In the drop-down menu that appears click the plus sign in the Zoom row until the text is big enough.

I completely agree because my teachers type their comments in Word and then copy and paste them into the comment field.  I have all sorts of different fonts and I never thought to tell them to use a specific font and font size when writing their comments.