Per the style guide, Flow should use mw-ui-destructive ("Use destructive buttons for actions that remove or limit, such as deleting a page or blocking a user.") for removal actions (i.e. hide, delete, suppress).

Currently, all permutations incorrectly use mw-ui-constructive:

Hide topic
Delete topic
Suppress topic

Hide post
Delete post
Suppress post

Lock could be argued either way (as it does limit, but it's also meant to be used in the normal course for concluded discussions).