When an archive file is passed to Dolphin via the command line, it doesn't try to show it using the appropriate KIO slave. Instead it opens the configured external application to do that.
This is a major problem if said application is Dolphin itself. In that case the newly opened instance of Dolphin will try to open the archive in yet another Dolphin, etc.
Steps to Reproduce:
1. Open a ZIP archive with "dolphin foo.zip"
Dolphin opens the archive in the configured external program, even if "Open archives as folder" is enabled and said external program is Dolphin itself.
If "Open archives as folder" is checked in Dolphin's config, it should do this. Otherwise it should open the archive in the configured external program if that is not Dolphin. If it is, Dolphin should do something more sensible than causing an infinite loop anyway.
I only tested this with ZIP files.
*** This bug has been marked as a duplicate of bug 318683 ***