After finally getting my IPv6 working nicely, it was time to prevent Transmission from using IPv6 as I don't want lots of torrent traffic going through the tunnel when it's faster through IPv4 (until a time I can get Native IPv6). Apparently this is an "invalid" feature request according to some of the developers. (http://trac.transmissionbt.com/ticket/4197)
Had the developer actually stopped to consider it, maybe read some relevant parts of the source code, they would have quickly discovered that you can already disable it! They could document it as a feature without having to touch a line of code, and mark the feature request as completed!
It's a rather simple fix. There are checks for the IPv6 address not being a link local address, or a 6to4, or Teredo tunnel. So we just make Transmission bind to a link local address and hey presto, no IPv6 for Transmission!
Simply add the following line to the settings.json file.
 You'd think given that they already prevent Teredo tunnels from being used, that the feature request would actually make sense for those wishing to disable IPv6 due to TUNNEL's!