When “public assigns” is enabled in the assign plugin, a regular user sees a drop down button which looks like they are able to reassign the topic. The button does not actually work though.
A movie clip says more than a thousand words, so see below. Brand new instance, no other plugins, latest tests-passed and assign plugin including all the latest fixes. Left window is an admin user, right window is a brand new TL0 user. The real action starts at 0:38.