Comm/Diff (or alternative) that respects glob characters: is this possible?

If you want to report all the lines of bar.txt that match none of the patterns in foo.txt, in zsh, that could be:

unique_lines=(${(fu)"$(<bar.txt)"})
unique_patterns=(${(fu)"$(<foo.txt)"})
pattern="(${(j[|])unique_patterns})"

print -rC1 -- ${unique_lines:#$~pattern}

Or all in one go:

print -rC1 -- ${${(fu)"$(<bar.txt)"}:#(${(j[|])~${(fu)"$(<foo.txt)"}})}

• $(<file) is the ksh-like operator that expands to contents of $file striped of trailing newline characters.
• ${(flags)param} uses parameter expansion flags to affect the param expansion.
• f flag, splits on linefeeds (here expands to the list of non-empty lines).
• u (uniq): removes duplicates. So ${(fu)"$(<foo.txt)"} expands to the unique non-empty lines of foo.txt
• ${array:#pattern} expands to the elements of $array that don't match the pattern. Here the pattern is constructed as:
• ${(j[|])unique_patterns} where the elements of $unique_patterns are joined with |. So we end up with a (line1|line2|...) pattern.
• The ~ in $~pattern causes wildcards to be considered as such upon the variable expansion.

Note that wildcard syntax is that of zsh wildcards. That's affected by a few shell options like extendedglob, kshglob, nocasematch...

In bash, you could do something similar with:

shopt -s extglob
pattern="@($(sort -u foo.txt | paste  -sd '|' -))"
sort -u bar.txt |
  while IFS= read -r line; do
    [[ $line = $pattern ]] || printf '%sn' "$line"
  done

This time, the syntax is that of bash extglob wildcards, similar to that of ksh88 ones.

Note that the order of the lines in bar.txt ends up being changed.