Last year, Blogger announced an exciting improvement in Blogger blogs - the ability to export and import blog content (comments / posts) between Blogger blogs (as long as you have administrative access to both blogs).
At the time, that was interesting, but not so useful, as only Blogger blog content was supported by the process.
Last month, Google announced an improvement on that possibility - the ability to export and import blog content between hosts outside Blogger.
Blogger now supports content transfer between Blogger, LiveJournal, MovableType, and WordPress. Hopefully, other blogging platforms will follow in availability.
If your non Google host is not directly compatible with Blogger, you may be able to use WordPress as a conduit. If you can import into WordPress, you can use WordPress2Blogger to convert to Blogger compatible content.
It's possible that both the receiving and sending platforms will have to make adjustments to their code, to enable additional platforms to be included.
Google now has a Google Group based forum, where you can get peer support for your questions about the export / import feature. They note that the conversion process is not known for accepting content with dodgy syntax.
With a blog of any significant size, it would be wise to import, then publish, in two separate steps. Get everything imported, and check out the Posts list under "Imported", before Publishing.
As of 2016/02), the Blogger "Export / Import" feature is now known as "Import & back up".
An Important Update
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