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Culturally it is generally frowned upon. It is a personal choice. I have a rule that I will only upvote my own posts if they receive downvotes with no explanation for the downvote.

However, once #vyb became a thing you were rewarded vyb for posts that you put in #pob or #proofofbrain and #vyb. Yet if you upvoted your own post you did not receive that reward in vyb.

It provides a good incentive for never up voting your own post. Now at the time that was done #vyb was worth a lot more in terms of financial value than it currently is.