There is no distinction here between new or old member. They will give you merit if they see that your post is useful for them.
The point here is will they read your comments or not. Specially when your comment is on a mega-spam threads like hundreds of pages. So your comment is likely a fish in an ocean and noone will give a shit about it. Stop telling people to make a high-quality post when the solution is making a HIGH-QUALITY POST in a NON-MEGASPAM-THREAD.