You have received a @GrumpyCat flag because you or someone else send money to buy votes on your post from an irresponsible non-GrumpyCompliant service.
Some bots like @sneaky-ninja (by @michaeldavid) are acting irresponsibly by selling votes on posts very close to final payout. These votes are sneaky, not promotion and are most of the time placed on low value content.
Sending money to these bots is also financially supporting for-profit only posters (spammers).
To know what voting bot to use, refer to https://steembottracker.com/ and use those that have 3.5 day or less in the "Max Age" column.
Important warning, since @sneaky-ninja has made no effort to improve in more than 4 months, it's vote will still be countered even should they improve his Max Age setting.