I get gibberish when I compile

I am compiling into .doc or .docx format and I get gibberish. For example:

How can I make it stop outputting my novel in some code?

It looks to me as though you chose a compile preset designed to deliberately generate gibberish (mainly to create an effective word count without uploading actual words to NaNoWriMo’s word counter). You could either choose a more suitable format, or delete the entries in the Replacements compile option pane (under the “Preset Replacements” tab).

Is it COMPLETE gibberish though? I can make out “…gave him a smile in thanks and went back to the front desk”. Surely if complete gibberish was intended it would be lorem ipsum type? This looks more like a substitutionary kind of thing, where the words and number of letters are preserved, but SOME of the letters are changed?

It’s not meant to be encryption or 100% secure if that is what you mean. It just substitutes a handful of common letters for other letters, with a few letters using the same target letter to make it so that it isn’t a completely reversible substitution cipher.