Not all of these kinds of posts are about Reddit. Since Lemmy is still a bit more quiet than Reddit, I find it more informative to browse All. It's a great way to find new communities, instances or create new filters.
The problem is when the same person blasts 10 or more communities with the same post. Depending on how your Lemmy client sorts posts, you may see all of those posts in a row.
I am all about spreading information far and wide, but I really try and submit posts to the most relevant communities. World news may be the only exception to that rule, since it can apply to many places.
I think it will take a little while before people adjust to the way lemmy works. It was fairly good practice to repost in multiple communities to spread info on reddit. The way federation works, this isn't strictly necessary anymore
On my main account (this is my alt while startrek.website purges the intake manifold) I just blocked the bots that repost reddit shit, and I go to different instances, find their local communities and sub. My lemmy is fricking vibrant.
I've seen a few references to this in the last couple of days, but I don't see it myself. On Firefox (and presumably on any browser) I just see one version of a crossposted thread, with a note at the bottom that links to the crossposts.
I think that's a sync issue as I've never had this issue before. However, if I go to browse similar communities I see virtually identical posts in the communities just not in my subscribed, local or all feeds.
Just like reddit, sorting by top 6 hour is a far superior experience to active. Otherwise you'll just see the same posts for literal days as long as it's still getting comments and votes.