I have no idea how this is controversial. Why is posting your own memes/comics worse than posting someone else's content?
You can see exactly why in this very comment chain, people talking about organising followers to boost things etc
The point of a link aggregator is not to act as veiled marketing for social media accounts or cosplays. Posting your own shit is 9 times out of 10 just promotional crap. Like this. Lemmy doesn't need content that exists primarily to drive traffic elsewhere, or shit content for the sake of shit content.