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If you set your rewards to burn on memes not of your own creation you can still get votes and boost your rep, but if you want rewards you are gonna have to restrict them to original memes only.
This is the content policy of the chain.
Setting your rewards to burn allows the voters to still get paid, only your rewards are burned.
Continued plagiarism for rewards will get your account downvoted to being behind a click wall to be seen.
Nobody wants that.

I always ask the creator if i could post their meme here.

Lol.
The community standards are as stated, up to you follow them, or not.

So im not allowed to post memes even if I asked the creator? lol

You can post anything you want, just decline rewards for things not of your own creation.
The standard for content on the chain is original content every time.
Profiting from someone else's work is not rewarded here.