I just leave my feed on All to see a bit of everything, but it drives me nuts when I see someone either post the same link in quick succession to 3+ instances at the same time, so they all end up next to each other on my feed, or you post several related posts (photography, articles etc) within a few minutes so your name and all your context blocks out a large chunk of the All feed, I downvote each post, then block you as a poster, and each of the instances as well. I understand cross posting and wanting to create content for the community is something you want to do to get the Lemmy ball rolling more, but spamming is just extremely annoying, regardless of the content.
Posting identical content to multiple communities is the definition of spamming. It creates more content, but not more new content, which could be argued has negative value on a federated platform like Lemmy. The first post has value; everything after is noise.