I really like FA or deviantART's system, where notifications are grouped by type. Under the current FN system, it's actually pretty hard to pick out comments from everything else; even if they messages were colorcoded, having them all appear together is overly complicated if you're a selling artist and are trying to locate/respond to sales inquiries. While I find it's useful to know if my newly uploaded work is gathering interest, I don't need to know who is clicking on it as much as who's asking to buy it!

As well as all the valid reasons against infinite scrolling others have listed above, it's also been proven to harm sales. My husband is in business intelligence and knows that when Etsy tried it out, their users were sent to either an IS version of the site or the classic paged version. In the IS one, sales were considerably less and as an artist who sells on sites like this I want to make it as easy as possible for people to buy my stuff!