"/\*" - literal forward slash followed by literal asterisk
  "(.*?)" - followed by zero or more of any character, captured non-greedy
  "\*" - and another literal asterisk

  "|" - all of the above, or the following

  "//(.*?)" - literal two forward slashes and another non-greedy anything
  "\r?\n" - a possible carriage return followed by a newline

  "|" - or

  the following pattern in double quotes:

  "(\\[^\n]|[^"\n])*" - a backslash followed by one character that is not a newline, OR anything that is not a double quote or a newline.  this sequence can occur zero or more times, and both the matching sequence and all of the matching sequence are captured

  "|" - or

  "@("[^"]\*")+" - a literal at sign, followed by one or more of anything that is not double quotes, enclosed by double quotes.

All it's doing is sniffing segments that look like they might be comment blocks, sections in double quotes, and... I'm not actually sure what the last segment would be, it seems to capture @"whatever"? Regardless, this doesn't actually sniff for ASCII art as much as comments themselves.