That definitely makes sense.
On the other hand, saying "greatly appreciated" is a term used for thanking someone. With that context in mind, saying "An upvote is greatly appreciated" is basically the same as thanking someone for an upvote. The general context of the sentence also implies that it is directed at everybody. Hence, it is still upvote begging in that they assume you are going to upvote and are trying to encourage it through semantics.