You’ve obviously never had comments like “Wow how has this project had 20000 views in 10 minutes?????”I'm not opposed to the suggestion at hand, but to be fair, most of these comments won't necessarily stop if the suggestion were implemented, right? It's pretty easy to miss any particular entry in the “What is Happening” and “What I've Been Doing” sections — and in comparison it is very easy to see that your reshared project is your most recently-shared project, so people may just assume that this is your newest project shared for the first time.
I do agree that it would be helpful to show when a project was reshared, but if your aim is to prevent these comments, I'm not sure this would be the solution. Perhaps a different solution is to, in the list of your projects on your profile, put the reshared project in the same place that it was when it was originally shared. But then there may be reasons why someone would want to “bump” a project to the top of their profile, so I'm not sure if that works either.