In the Father Christmas letters too there is sometimes a space (in the manuscript) before exclamation marks (see, e.g., pp. 43 (top), 65, 68, 71, 76, and 94 of the most recent edition), though this is not consistently done (compare pp. 43 (bottom), 51, 64, 72, 84).
What's more, it isn't just exclamation marks. Tolkien tends to put a space before other punctuation as well. He does so very frequently with semicolons and colons (respectively at least 28 times and 41 times up to 1933, where I stopped counting), and similarly with commas and periods (which I have not counted, but they have a space more often than not), as well as parentheses (pp. 97, 101, etc.), apostrophes/quotation marks, and question marks (ibid.).
What's more, it isn't just exclamation marks. Tolkien tends to put a space before other punctuation as well. He does so very frequently with semicolons and colons (respectively at least 28 times and 41 times up to 1933, where I stopped counting), and similarly with commas and periods (which I have not counted, but they have a space more often than not), as well as parentheses (pp. 97, 101, etc.), apostrophes/quotation marks, and question marks (ibid.).
Philomythos Thank you for the awesome references!