Hi Ian! Sorry for a so long delay (though you've replied only to the bug email address, so I'd never receive notification).
If you think that newer chiark-tcl still can be built on older Debian systems (woody and older) then it's OK to keep tcl8.3 in build dependencies. And you can lose the bug. Cheers! -- Sergei Golovan -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org