Commented code blocks the rule

Hi,

I know this seems really strange but here is the behavior I get from several rules using the "After saving new content" condition and a "PHP custom code" action:
A soon as I put the proposed variable $referenced_node (proposed in the "PHP Evaluation" fieldset, but this variable was created in another rule) inside php comments (both // or /*), then the rule breaks, it's simply not read.

I can't see how commented code can break a rule, but I'm 100% sure of this. I tried removing simply the $ of the variable and the rule works.
So putting
// $referenced_node
breaks the rule, and
// referenced_node
does not, for example.

I struggled for hours before spotting this (who would think that removing a comment will change the output...). Any idea where the bug could come from?