Group permissions are broken?

[Yuri]

On 08/16/2011 01:32, perryh at pluto.rain.com wrote:
> On my 8.1 system, sticky(8) says:
>
>    A directory whose `sticky bit' is set becomes ... a directory in
>    which the_deletion_  of files is restricted.  A file in a sticky
>    directory may only be_removed_  or_renamed_  if ...
>
> [emphasis added]
>
> Nothing there about the sticky bit changing the permissions required
> to_overwrite_  a file, which is the subject of the current inquiry.
>
> Even if the sticky bit_did_  have some effect on overwriting a file,
> how would that explain the_different_  behavior of the two cases shown?

Actually, sticky has nothing to do with this. I originally spotted the 
problem on one device under /dev/ and later just made an example under 
tmp. Same behavior was for any other directory.
I still can't get why this happened.

Yuri