Before we go too deep down the rabbit hole, let's tackle the terms that you highlighted:
- directly preceded or followed by a number
- followed directly by a lower case Latin letter
- preceded directly by a lower case or upper case Latin letter
May I propose that instead of meaning "unspaced in print", these terms mean "without an intervening symbol or indicator in braille" (e.g., capital indicator, grouping/enclosure sign, alphabet indicator, level indicator, fraction indicator, etc.)? If that is the meaning of these terms, does that affect your confusion?
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Thank you for sharing your thoughts! I look forward to your response.