The default commit message for tag is hard-coded. If it was configurable, we wouldn't have to -e or -m every tag operation (or create a command alias) to use a different template.
Mercurial do in general have sane defaults and do not have knobs for customizing them. Mercurial will thus in most cases behave the same way on all installations. We like that. Why can you not just use an alias or wrapper script as recommended on the mailing list? Why do you want to customize the tag message in the first place?
The default message doesn't suit my style. More significantly, non-English speaking organisations may want a default commit message in their local language. Hard-coding such strings has been considered bad practice since before many hg users were born.
Won't fix, closing. This feature doesn't quite cross the usefulness threshold. It's just as easy to apply one of the existing work-arounds as it would be to configure a new config options, and only one person in 7 years seems to care.
--- Bug imported by bugzilla@serpentine.com 2012-05-12 09:29 EDT --- This bug was previously known as _bug_ 3328 at http://mercurial.selenic.com/bts/issue3328