I couldn't really find the right words for a concise question title, so here it is in full: Let's say I am going around on the site and see an answer/question that is not great, maybe it doesn't help a ton or could have been found with a bit of research, but it has correct conventions of English and the poster seems to have put in effort. It is massively or even moderately downvoted, for (to me) apparently no reason. Can I upvote it to cancel out two of those downvotes (because an upvote is +5 and two downvotes is -4) not because it is great and deserves an upvote but is simply okay and doesn't deserve downvotes? I sometimes feel bad when I see an answer, like the bottom answer on this question, which is simply discussing something the poster feels on a discussion tagged question, and is not off topic, useless, or otherwise bad for the site, downvoted so heavily that I give an upvote just to even it out, because I don't feel it deserves that much punishment. Maybe one downvote but 13 seems way overkill.
Can I upvote it to cancel out two of those downvotes (because an upvote is +5 and two downvotes is -4) not because it is great and deserves an upvote but is simply okay and doesn't deserve downvotes?
No. Upvotes and downvotes should be used based on content only. Voting based on current score is... problematic, to say the least. An answer currently scoring -2 could very well rise up to 0, and if you'd already upvoted it, the score would be +1. If it's not a very good answer, then it shouldn't have a positive score.
Additionally, the answer you linked to is on a meta site. Votes on meta do not affect reputation, and, in the case of feature-requests and certain discussions, voting indicates agreement or disagreement with the proposal rather than quality or usefulness of the post.
If you like the idea the answer expresses, upvote it. If you don't like the idea, downvote it. If you can't decide, don't vote at all. But however you decide to vote, current score should not be taken into account.