When not all information is supplied to perform an action in the MCP, any post selection made is lost. For example, when planning to split certain posts from a topic, and selecting those posts, but failing to supply a title for the new topic, the board will (of course) display an error notice when trying to perform the action and not perform the action. The post selection is reset to all posts in the view selected.

This is true for splitting from selected post, splitting selected posts, and merging selected posts to a different topic (in case no target topic was supplied).

A moderator might end up moving more posts than intended. Possible solutions are to make the default to be all posts unselected (the moderator will get a notice to select posts) or preferably, to retain the post selection.
will have been reset to is going to split a topic, and making a selection of posts to split (or split from), but failing to supply a title for the new topic, the board will (rightly) complain a topic needs to be selected.

However, the selection of posts that was made has been lost. If the moderator does not notice this, he/she may end up splitting more posts than planned, because the default of the view is for all posts to be selected.

I presume the