Hello,
I just wanted to report on Sitemap plugin... When the tag URLs are included in the sitemap they are not valid if the plugin path has been changed on s9y's permalinks in the configuration.
i.e. /plugin/tag/Tagname is used on Sitemaps plugin even if the URL for plugins is changed to /plug/ or in our case /en/
In our case, Google sitemaps showed hundreds of errors related to this... Google is not happy with all of those 410 redirects we made if the URLs on sitemaps are the links we redirect from and not the real destinations.
In case of entries, sitemap plugin shows correct URLs even when permalinks are not default.
Have a nice day!
Mel