When doing open source development it's normal to track against the upstream for a period of time while doing any changes on a topic branch. One of the things I have noticed when bringing the upstream back is that a merge commit is created. If I then create a pull request this merge commit ends up as part of the PR.
My question is, is there any harm in this? I have read that some people feel they are useless but I like the fact that they act as a timestamp against when I last synced with the upstream. Is there an accepted practice for tracking the upstream and introducing merge commits.