It is probably going to late to add my suggestions (if you ever have the intention to put them) on the next release but it would be good to consider adding a couple of features to both Thank you and Groan hacks.
IMPORTANT I would add on the user profile a search options to find out which posts X users has either groaned or thanked. I had I look my self but the query would be too complicated for my level

. This is important, because immature users tend to abuse from the system either over thanking or over groaning (specially the second one). This feature would make finding this guys much easier.
Another interesting option would be allow X user-groups (defined on acp) to delete all groan/thanked (in one post) instead of hardcoded.
(this one might be in this upcoming version but still...) Number of groaned or thanked posts updated via AJAX.
Add a confirmation when you are going to delete all the thanked or groaned from one post.
In my forum I also added a nice little feature so u can compress who has thanked or groaned a post, this way, good topics are not interrupted when a post is thanked/groaned. (Couldn't get it to use just one image to compress and decompress the table, still... it works xD) [see attachments](PS sorry the buttons are in Spanish, one says "praise" (green) and the other "criticize" (red) and the Chinese things go with the site topic)
Another thing (if reputation activated) I've came to notice is that when you give a thank or groan to a post, afterwards if you try to give reputation to it you get an error message saying this post has already been given reputation, but if you give the reputation first, then you can thank or groan. Maybe this could lead to a db corruption, maybe is harmless, or it was done in purpose so you can do both ^^.
It would be cool to use decimals instead of whole numbers for the reputation feature, put I guess it requires a lot of db changes and of the system it self which would make it a pain in the ass to do.
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Besides that, the hack is a joy to have. Will be anxiously waiting for the new versions ^^