The tooltips on all sites, including Meta sites, currently read as follows:
- Question upvote: "This question shows research effort; it is useful and clear"
- Question downvote: "This question does not show any research effort; it is unclear or not useful"
- Answer upvote: "This answer is useful"
- Answer downvote: "This answer is not useful"
This does not fully represent how voting works on meta sites, which leads to confusion and frustration among new users unfamiliar with Meta voting culture when they receive downvotes.
Per Can we re-request features that were declined a sufficient while ago?, I'd like to revisit this, for a few reasons.
First and foremost, it's clearly a well-received request: the proposal itself is at +197, the answer agreeing is at +126, and Jeff's answer declining it is currently at -56 (making it the 17th most downvoted MSE answer of all time).
Second, the meaning of votes on Meta sites has become pretty well established among regulars: agreement/disagreement with feature requests, bug reports, and the premise of discussions.
Finally, the Stack Exchange network is much larger than it was 10 years ago: expecting people to know that the tooltip on the downvote button is a bit misleading and to look somewhere else for the full explanation just doesn't scale. It's an extremely common occurrence to see posters comment asking, to quote an example from a recent poster from Meta.SO, why downvoters are "classifying this question as not showing 'any research effort,' being 'unclear' and/or 'not useful'."
As far as the actual text of the tooltip, I'd suggest something a bit broader than the simple "I agree"/"I disagree" that was proposed in the original request. I do agree with Jeff that that would be too limiting. I would suggest something along the lines of "This question is unclear, not useful, or I disagree with what it suggests" for the question downvote tooltip.