David Gerard, 10/01/2014 22:02:
However, being able to thank IP contributors for their contribution would be FANTASTIC. Saying "thank you" to casual drive-by contributors would give them quite a buzz, I'd think.
You already can, even on the unwelcoming ;) en.wiki and de.wiki: talk pages have not (yet) been killed. I think about 30-50k persons have been thanked with the simple {{grazie}} template on it.wiki across the years. https://meta.wikimedia.org/wiki/Cross-project_comparisons#Thanks
Perhaps a timeout? Say, you can thank an IP for their edit within 1 hour? We can experiment and see what time gives the best amount of thanks versus mistakes.
On it.wiki, anonymous talk pages are purged monthly (with some conditions).
Nemo