Could not un- and re- link ~/.subversion/config

Hello the list,

I just lost a few hours trying to do this:

$ cd ~/.subversion
$ rm -f config
$ ln -s /path/to/another/config .

The link command kept failing, because "File exists"
   WTF ?

Turns out I cannot remove ~/.subversion/* in one command, as some other process is protecting them from deletion (but not from editing).

Eventually I did figure out the workaround, which is simply to join them into one command
$ rm -f config && ln -s /path/to/another/config .

But it was a £*({ing annoying few hours between problem arising and finding solution (and even more annoying that the solution was so simple)

I can find no documentation of this feature at
    http://svnbook.red-bean.com/en/1.5/
    http://subversion.apache.org/faq.html
    http://mail-archives.apache.org/mod_mbox/subversion-users/
so, I would like to ask:

a) where is it documented ?
b) can it be extended to other user-configurable directories ?

Thank you for reading this far, and any writing you might be able to do.

-- 
Alan