Sometimes the specifics take a bit of time to determine and we don't always know who the newbies are so just give higher level instructions. In this case it's a matter of using a tool like Firebug to determine the CSS selectors and then craft some CSS to hide the arrows.
So I activated Jetpack and Montezuma on my test site and set up the sharing. Then went to a post and played with the CSS in Firebug to see that the following should hide the arrows.
HTML Code:
.sharedaddy i {
display: none !important;
}