[carmenchu]

Well, attached is a new version, with:
- Option 'no tags' removed--it couldn't even be reported, lacking a list of tags for reference.
- Added a message (Qt) with buttons to choose on the fly if run only for reports (default -> OK) or to apply the changes (Cancel).
That would be useful before choosing to add/remove tags from preferences.
- Changed the versioning: this is v1_0, (implicitly making previous ones 0_x)
- Automatically sort the tag list (easier to inspect/edit), besides trying to ensure that it works.
Unfortunately, as it MUST be a comma-separated list, without spaces, the code is quite clumsy. A less unwieldy alternative would be appreciated.

Spoiler:

# protect editable string from mistype
def sanitize(string):
    if string != (' '):
        string = string.replace(' ','')
        string = string.replace(',,',',')
        string = string.lower()
        lstring = string.split(',')
        ostring = sorted(lstring)[0]
        for s in sorted(lstring)[1:]: # list of comma-separated strings
            ostring = ostring + "," + s
        # MUST be list of words(=tag names) comma-separated & without spaces
        string = ostring.replace(' ','')
    else:
        string = ' ' # Avoid bk.savePrefs(prefs) deleting the "tags" entry?--general havoc
    return string

* Query: are buttons of the message easy to understand, o rather counter-intuitive?