The old "a coach can't touch a runner" thing is one of the most enduring rule MYTHS in baseball and softball, probably right up there with "the hands are part of the bat". I can remember dust ups about this when I played youth baseball and that was a looong time ago!
Live or dead ball makes no difference. There's no rule that says a coach can't touch a runner. A coach may not physically assist a runner in her efforts to run the bases while the ball is live. Examples of assisting include, but are not limited to, grabbing the runner to stop her advance, pushing the runner toward a base or helping her up after she falls. A congratulatory hand slap should not be considered as an assist.
The college game where the defensive team helped the injured runner around the bases may have created a warm and fuzzy feel-good moment, but the umpires for that game actually got themselves into some hot water from their supervisors.
First, they told the offensive coach that if the injured runner could not advance beyond first base on her own that she would be credited with a single. That was incorrect as there's no rule denying the four-base award for a home run.
That was strike one.
Next, they denied the injured player a substitute to complete her home run base award. The rules actually allow a sub in this situation.
That's strike two.
By forcing the injured player to be carried around the bases, they exposed her to the risk of further injury by being jostled around and dropped on each base.
And...that's strike three!