I agree; this seems broken. Small test case...

use strict;
use warnings;
use Test::More;

{
    package Thing;
    use Moose;
    has attr => (is => 'ro');
}

{
    package ThingWithRef;
    use Moose;
    has attr => (is => 'ro');
    sub translate_to_dutch
    {
        my $self = shift;
        ${ $self->attr } =~ s/e/a/;
    }
}

my $obj1 = Thing->new(attr => 'Hello');

my $obj2 = ThingWithRef->new(attr => \$obj1->attr);
$obj2->translate_to_dutch;

is($obj1->attr, 'Hallo');
done_testing;
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If you use Moo instead of Moose, then things work as expected.

UPDATE: OK, not a bug. It's just that the reference \$obj1->attr is not guaranteed to be a reference to the slot within the object. So changing data via the reference will not necessarily effect $obj1. If it works, it works; if not, then it won't; no guarantees. Currently it works in Moo but not Moose, but the situation - in either - could change.

If you want what you want (for both objects to have access to the same piece of data) then you need it to be a scalar ref in both classes.

UPDATE 2: It also fails in Moo if Moo is in pure Perl mode (not XS).