Perhaps the response should not return raw HTML:
# curl https://simplekv.com/path/to/key2
<html><body><h1>Well, this seems safe...</h1></body></html>
# curl https://simplekv.com/path/to/key2
<html><body><h1>Well, this seems safe...</h1></body></html>
I guess this argument could also be applied to Pastebin? Should it be returning raw HTML if asked to?