On second thought... using the development version, I notice that the mixed sitemap with all languages in one, in combination with a page as homepage, has the following effect:
The xml sitemap always starts with the main URL and then starts looping through pages and posts. During this loop, there is a small check to see if the page that is in the loop is not set as front page. If so, that URL is skipped because it will be the same as the main site URL at the start of the xml sitemap. This check is done with
if ($post->ID == get_option('page_on_front'))
However, in the mixed (un-languaged) sitemap, this check does not work. You can see the effect on http://valentheze.fr/sitemap.xml ... Whether this is actually a problem (different URLs but same content == duplicate content) or not, I'm not sure. On the single-language sitemaps, it does work just fine since the home URL gets translated to the corresponding page URL. See http://valentheze.fr/sitemap.xml?lang=fr (or =nl or =en)
So now I'm hesitating: use the mixed sitemap and try to fix it, or use the single-language sitemaps and fix it so that the main sitemap redirect to the default language sitemap... Both are viable options. What do you think is best?
Two other things I noticed using the Polylang dev version:
1. The home page redirection seems a bit messed up on http://valentheze.fr/ :
When I visit the site in a Dutch browser, I get redirected to http://valentheze.fr/nl/ and see a blog page listing latest posts instead of the static home page http://valentheze.fr/welkom/ ... Same for other languages. I do not want this (I did not set a static page as front page for nothing ;) ) so I check the Languages option 'Redirect the language page to the homepage in the right language'. I'd make this option default but it has one downside: since it does not actually redirect but instead show the front page content, we've now got a duplicate content issue :(
Unless I check 'Hide URL language information for the default language'...
2. Next, still with the 'Hide URL language information for the default language' option unchecked, I browse to the French homepage. This time, trying to get back to the Dutch homepage via the flags, it turns out I get redirected back to the French homepage!
Unless, again, I check 'Hide URL language information for the default language'...
Would it be possible to get rid of these 'language pages' ( /en/ , /fr/ , /nl/ etc. ) completely?