When I look at edits that anonymous users have made, there is no link to thank them.
Some really good contributions are made by IP users and I don't see the reason for not being able to thank them for it.
* [[https://en.wikipedia.org/w/index.php?title=Wikipedia:Village_pump_%28technical%29&oldid=656939862#Sending_thanks_to_IPs|w:en:Wikipedia:Village pump (technical)#Sending thanks to IPs]]
This card tracks a proposal from the 2015 Community Wishlist Survey: https://meta.wikimedia.org/wiki/2015_Community_Wishlist_Survey
This proposal received 41 support votes, and was ranked #22 out of 107 proposals. https://meta.wikimedia.org/wiki/2015_Community_Wishlist_Survey/Notifications#Modify_.22Thank_you.22_so_we_can_thank_anonymous_editors