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I wouldn't say so. Maybe it depends on the settings used, but honestly I don't know too much about it to be able to give a proper answer 😂

I think it depends on how frequently it's used and then what happens to the rewards. Doing a contest? Nothing wrong with it. The odd post for full liquid payout? Totally fine too.

Using it on every post? Probably will attract unwanted attention/reduce your likeliness of curation

No. On Hive there are great debates about whether people have the right to do what they want with what they earn. Not everyone will curate you if you use reward.app, because they think HP should be left in the system to support Hive's value ... but it is still your choice.