[Leonatus]

The indent (spaces) is important.

I tried to make it as you proposed:

Un-Force user font-family in KePubs:
  - Enabled: yes
  - Description: |
      The KePub reader uses a very heavy-handed method of setting the font selected
      by the user, overriding all fonts set by the publisher in the book unless
      "Publisher Default" is selected.
      This patch lets the font-family set by the publisher in the KePub stylesheet
      override the font-family selected by the reader from the device in some
      cases, which allows a mix of user-selected and publisher-selected fonts.
      Alternatives 1-3 give increasing preference to the publisher-selected fonts.
  - FindBaseAddressString: "* { font-family: %1 !important; }\n"
    #
    # Alternative 1:
    #     * { font-family: %1 !important; }\n
    # --> div,p{font-family:%1!important; }\n
# - ReplaceString:
#     Offset: 0
#     Find: "* { font-family: %1 !important; }\n"
#     Replace: "div,p{font-family:%1!important; }\n"
#     MustMatchLength: yes
   #
   # Alternative 2: (Similar to ePub default)
   #     * { font-family: %1 !important; }\n
   # --> body,p{font-family:%1!important;}\n
 - ReplaceString:
     Offset: 0
     Find: "* { font-family: %1 !important; }\n"
     Replace: "body,p{font-family:%1!important;}\n"
     MustMatchLength: yes
    #
    # Alternative 3: (similar to ePub with `Un-force font-family override p tags`)
    #     * { font-family: %1 !important; }\n
    # --> body{font-family:%1 !important; }\n
# - ReplaceString:
#     Offset: 0
#     Find: "* { font-family: %1 !important; }\n"
#     Replace: "body{font-family:%1 !important; }\n"
#     MustMatchLength: yes

but with no result. Shouldn't the values be set to "y"?