You can move Microblog posts by sharing the post the new channel and disassociating it from the old channel.
To share the post, add a new comment and either add the hashtag for the new channel, or select the new channel from the "+" menu next to the "Did you want to share this?" option. Once the comment is published the post will be shared in both channels.
At the top of the post to the right will be the list of channels the post is shared in. You can now removed the post from the old channel by selecting the "x".
Please let me know if you have any questions,