This idea is pretty old, proposed by one of the guys during the python mockup days. Now that Leaftag - http://www.chipx86.com/wiki/Leaftag - seems to become the default mechanism, we may reconsider this for Thunar. Adding basic support should be very easy and it's really worth it in a modern file manager.
Moving to 0.4.0rc1. Tho, I doubt that it will make it for rc1.
Moving to 0.5.0rc2.
Definitely not for rc2.
Moving to 2.0.0final.
Close bug reports of archived products.