I’m pretty sure that the order of the Meriter names on a given post is based on these three factors in the following order of priority:

1. Total number of sMerits (he could have merited it more than once) awarded to to the post by the profile (descending order).
2. Activity of the profile (descending).
3. Registry date (oldest first).

Therefore, if two or more profiles have awarded the same number of sMerits to a given post, the leftmost name will be that with most Activity. If even so two or more profiles have the same Activity, then the leftmost will be the profile that was registered first.

That means that activity changes alone modify the order.