[ADDENDUM] File permission confusion [Debian 9.1 with MATE]

[Richard Owlett <rowlett@cloud85.net>]

On 01/01/2018 05:23 AM, Richard Owlett wrote:
> As user "richard" I created 3 files.
> I later wanted to protect them totally from accidental change.
> For each file, I went to Properties->Permissions and changed Access for
> Owner, Group, and Others to "Read Only".
> As user "richard" I was able to delete them with Caja.
> *UNDESIRABLE*
> As "root" I changed Owner and Group to "root" leaving Access for all as
> "Read Only".
>
> User "richard" could still *DELETE THEM*!
> "Read Only" evidently does not mean what it implies.
>
> What's happening?
> TIA

Logged into Debian as "richard" SeaMonkey was able to change contents of 
those files.

HELP!
That is EXACTLY what I was trying to prevent.