Does Linode support reverse DNS records for IPv6 addresses for nodes whose domain is not hosted at Linode? I was able to configure reverse DNS for the node's IPv4 address with no trouble (once I found the form hiding under "Remote Access", after being very confused by "DNS Manager" not seeming to support the setting of individual reverse DNS records ) but I can't find any way to do the same for v6. This node might conceivably send mail in the future, so I want to make sure its DNS is exactly as it ought to be.

Yes. Create an AAAA record for the hostname, wait for your nameservers to update, then put the hostname into the same box that you used to set up IPv4 reverse DNS records.

There has been an AAAA record for some time.

$ host ehwaz.owlfolio.org.
ehwaz.owlfolio.org has address 50.116.54.240
ehwaz.owlfolio.org has IPv6 address 2600:3c03::f03c:91ff:feae:edc9

But when I put the hostname into the "forward lookup" box on the reverse DNS page, it only reports the IPv4 address.

Hi,
I also had this problem and my domains were being hosted on Linode's nameservers. I ended up opening a support ticket and they took care of it for me.

Blake