differentiation for embeddings without a visible placeholder

[al_9x]

It would be helpful if in the blocked objects menu, entries lacking visible placeholders, were marked/labeled/highlighted. Is it possible to detect this (no visible placeholders)?

[Giorgio Maone]

Yes, it would be helpful.
Unfortunately NoScript does try to make placeholders as visible as possible (e.g. by forcing a minimum size), so when it fails it's hard to detect.