To make it more difficult, when I was trying to figure out the forum escaping on another thread, I was trying to get it working in code blocks. For some reason, those seem to use a completely different progression, and other numbers don't seem to be affected:
\1 - \1 -
\2 - \2
\` - ` -
\\2 - \2
\\\1 - \\1 -
\\\2 - \\2
\\\` - \` -
\\\\2 - \\2
I eventually wound up separating the backslashes with a zero-width space (U+00A0), and putting up a warning that it should be typed -- not copied -- into the Picard script. I'm not actually sure there's any way to format an even number of slashes followed by a one in code here, as even <tt> tags have that issue.
EDIT: Found a way to do so, at least for the inline code blocks: put two of the graves between the slashes and the number (`\\``1` results in
1, but the string to get the first, non-code-block display there is rather horrific). Not sure how to get that working with the full-line code indenting, though.