If it leads to anyone subscribing to a tag (like technology) would get posts from all instances in the Lemmy network tagged with technology, it would make it much better for all smaller instances to get an audience without posting to the larger ones.
This is in my opinion how it should be implemented, so it’s not important where a community is stored.
But if its just a way to tag posts with several tags, it may lead to posts being really spammy in nature, and everyone using 5 tags on each post. I think mastadon posts here on Lemmy are already a bit spammy.