You can remove the button styling via css to turn it into plain text. something like…
div.activity-meta .acomment-reply a {
background: white;
background: -moz-linear-gradient(top, white 0%, #FFF100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,white), color-stop(100%,#EDEDED));
background: -webkit-linear-gradient(top, white 0%,#FFF 100%);
background: -o-linear-gradient(top, white 0%,#FFF 100%);
background: -ms-linear-gradient(top, white 0%,#FFF 100%);
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#FFF',GradientType=0 );
background: linear-gradient(top, white 0%,#FFF 100%);
border: none;
}
ETC.
You can also use CSS to remove the avatar
.activity-list .activity-content .activity-header img.avatar {
display: none !important;
}