The real problem is that from inside _arguments, the -Q option gets
passed to compadd. Removing it is a fairly easy change. But I wish I
knew why it was used in the first place.
The first use of -Q in _arguments happened sometime between workers/7450 and workers/10309, which (unfortunately for quick back-tracing) were all slurped in as a single commit by PWS when we first migrated to git. At that point Sven was still doing 99% of the edits to completion and his entries in ChangeLog are a bit terse.