I was about to go for it as well.
This is what is says;
Requesting an increase to your credit line is easy. Tell us the amount you would like your credit line to increase by and provide some of your employment and financial information to help us with our decision. This request may also require us to pull a credit bureau report, which may affect your credit score.
So, if I put the information in as requested it will tell me for sure if it a HP on the next screen if not auto approved or a counter offer given ?
I've always requested my Discover CLI's through an agent b/c they will specifically tell you after they gather your information if there is going to be a HP or not, I've only tried on the web site a couple of times and get the HP message, but I know others who have been given CLI's wo the HP.