We're seeing a problem with Blogger Hosted Comments - and "Bad Request Error 400", following the use of the comment "Preview" feature. When a blog owner or reader composes a long or important comment, use of the Preview feature is normal. Right now, after hitting "Publish", following a successful Preview, one frequently sees the bad news. Bad Request Error 400 There is a workaround for this annoyance - and it's not difficult to use.
What Blogger won't tell you