I noticed some of my upvotes will take away from the rewards of certain users. I find this to be the case when there rewards are small like 1 SBD it will drop by a small amount. Once I saw my up vote bring a 1 SBD post to 0.12 and it made me feel like a horrible human being, just because I genuinely liked a post. The opposite happened on larger posts with several thousand where I saw the value went up by 10-15 SBD. If I see my up votes take from the value I think I will just remove it.
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From @themax37