Change style of comment form button

Is it possible to change the style of the “Submit comment” button in the post comment form?

I managed to style the Subscribe button targeting the following CSS element:

#subscribe-submit input[type=submit] {
/* custom style here*/
}

You can see the result on the sidebar of this page (the white/green “Lá vai!” button): http://www.ufrgs.br/intervires/exemplo-de-noticia-01

Now I’m trying to do the same with the Submit comment button, targeting the following CSS element, with no success:

#comment-submit input[type=submit] {
/* custom style here*/
}

You can see from the page I provided above that the Submit comment button is still gray/default (not the Reply button, but the one in the comment form, at the end of the page).

Thank you in advance.

https://wordpress.org/plugins/jetpack/