How do I comment lines in .plist file?
Syntax of plist is pretty much like XML, so you can use XML style comments.
<!--<dict> <key>Hello</key> <string>World</string></dict> -->
Xcode seems to believe that the <comment> tag corrupts the data. It will also strip out XML-style <!-- comments --> when viewing the plist in Xcode. It seems that a string entry, e.g.
<key>Comment</key><string>My comment</string> is the only way to reliably persist the comments.