If you are copying and pasting from one area to another, you might not be happy with the font, text size, or something else about the way it is formatted. This is particuarly common when copying from a source outside of Karbon, and pasting it somewhere into Karbon.
In this case, it will help to paste into Karbon without formatting.
You probably already know the keyboard shortcut for Paste (Mac: command-v, Windows: ctrl-v).
The shortcut for Paste Without Formatting is easy to remember. Just add the Shift key. (Mac: command-shift-v, Windows: ctrl-shift-v).