import re
rx = r'(/\* \s *ABCD[^*/]*)\* /\s */\* \s *Comment[^*:]+:(\s *\[ \[ [^][]*]]\s *\* /)$'
text = "Some text ... /* ABCD X 1111 */ /* Comment 1111: [[reason for comment]] */\n More text here... Some text ... /* ABCD XD 1222 */ /* Comment 1112: [[reason for comment 2]] */"
print ( re .sub ( rx, r'\1 #\2 ' , text, flags= re .M ) )
aW1wb3J0IHJlCnJ4ID0gcicoL1wqXHMqQUJDRFteKi9dKilcKi9ccyovXCpccypDb21tZW50W14qOl0rOihccypcW1xbW15dW10qXV1ccypcKi8pJCcKdGV4dCA9ICJTb21lIHRleHQgLi4uIC8qIEFCQ0QgWCAxMTExICovIC8qIENvbW1lbnQgMTExMTogW1tyZWFzb24gZm9yIGNvbW1lbnRdXSAqL1xuTW9yZSB0ZXh0IGhlcmUuLi4gU29tZSB0ZXh0IC4uLiAvKiBBQkNEIFhEIDEyMjIgKi8gLyogQ29tbWVudCAxMTEyOiBbW3JlYXNvbiBmb3IgY29tbWVudCAyXV0gKi8iCnByaW50KCByZS5zdWIocngsIHInXDEjXDInLCB0ZXh0LCBmbGFncz1yZS5NKSApCg==