I threw a program together to add information to Radare2 disassembly listings: radare2-listing.py. I’m putting it in beta, because I hope there is another way to do this in Radare2 (e.g. without a program). So if you know of a better way to do this, please post a comment.
The tool looks for text pushed on the stack, and then adds a comment with the string build up on the stack.