I understand what you need, I have experience with scrapping and testing webpages with a headless browser, which it is basically what you need.
I know the drawbacks of this program, if you want to do it in only one site maybe we can find a better solution for performance, instead of using a browser to actually click and insert the comments, but for that I will need to look on the website.
I can do it with Node.js and Zombiejs with a simple interface in HTML for you to enter the parameters, that way it can work with any site you want, but as I said losing a little in performance.
ZombieJS provides ease change of the UserAgent (what identify the browser) and HTML manipulation, suck as clicking and entering text on inputs.
If you need something else, contact me