I'm not sure where you want to add those lines exactly. There's a lexicon key "quip.email" used for the label.
If you want to change something in the template itself:
1) Copy the default form-template from Quip in a new Chunk
2) Make your modifications
3) Use that new Chunk as template in your QuipReply-Snippet with the "&tplAddComment" parameter
The default Form Template is here:
http://rtfm.modx.com/display/ADDON/Quip.QuipReply.tplAddComment