As a counter to that, GitHub had a very bad problem with that before they added emojis to issues/PRs. There were hundreds and hundreds of issues with countless "I agree" messages across major projects.
In that case, some moderation (manual or through automated tools) could be used to address the issue.
On that note, I noticed that my original post was downvoted. I personally think that it would be more useful if the person who downvoted it had posted a reply instead and detailed the reasons they disagreed with what I posted earlier (like you did). The latter contributes to the discussion. The former doesn't really provide any useful information other than someone out there disagrees with me and I have no insight as to why.
