Your effort could've been spared by asking the community for good solutions of the "Thanks"-commenting problem before implementing anything, just like Andreas pointed out in a comment.

I like the idea to change the tooltip of the upvote to "Thank and upvote", just like Caius Jard pointed out in another comment.

This is probably not enough to reduce the thank-comments significantly, so additionally you could display a little blocking popover when commenting any answer that is short and contains "thank", "thx" or whatever, too.

This popover would recommend the user to upvote instead and it would contain a button "comment anyways" to bypass the block.

Your effort could've been spared by asking the community for good solutions of the "Thanks"-commenting problem before implementing anything, just like Andreas pointed out in a comment.

I like the idea to change the tooltip of the upvote to "Thank and upvote", just like Caius Jard pointed out in another comment. This should be applied to upvotes for comments, too.

This is probably not enough to reduce the thank-comments significantly, so additionally you could display a little blocking popover when commenting that is short and contains "thank", "thx" or whatever, too.

This popover would recommend the user to upvote the post/comment, instead. It would also contain a button "comment anyways" to bypass the block.