If I file a new bug, after the field <tt>EMail:</tt> there is a hint, that the email address would not be publicly visible. But it seems to me, that the email address becomes visible if I clone the whole repository and examine the tickets and checkins afterwards via e.g. the timeline.

I have no proposal how this could prevented. Cloning tickets is IMO a good idea, but of course all data will also be cloned with them! So perhaps the solution would be to remove the <i>Not publicly visible</i> hint?