Why do the URLs of posts here change?

[Chris Angelico]

On Sat, Jan 10, 2015 at 3:52 AM, Rustom Mody <rustompmody at gmail.com> wrote:
> Is it?
> Ok lets test that.
> This is posted from google-groups.
> After posting I shall remove it

Remove it from GG, maybe, but I doubt very much it'll be removed from
the python.org archive. It's virtually impossible to remove something
from everywhere... you have to find every copy and hope none have been
web-archived yet.

ChrisA