I have a very hard time believing that an internal combustion engine would sustain significant damage prior to stalling. An engine could run, albeit very poorly, with extreme backpressure (say, an exhaust blockage but perhaps some leaks elsewhere in the exhaust system). If the exhaust was perfectly sealed, there would be so much backpressure that the mixture would be starved of air and there would simply not be any explosion in the cylinders. I have limited knowledge of diesel engines but would expect a similar result.

Here’s a video where an exhaust pipe is plugged. You can see how quickly the car stalls (at 10:00): https://piped.video/watch?v=jnoW0skAChA

It's a valid point that it could potentially create some confusion when a user assumes that everything in Signal is secure. Unencrypted SMS threads could contain an open padlock icon and even an ominous red window border, but someone inevitably will not understand the difference.

However, my frustration has been how both convenience and security is reduced by removing SMS from Signal.

Many people will continue to use SMS for a variety of reasons, necessitating the use of an additional app. So now we have people continuing to communicate over this insecure protocol, but with the additional target vector of potential vulnerabilities in the supplemental app.

Imagine a world where we can adopt a scalable, secure, open communication protocol where users can use whatever app they want. Imagine humanity moving past the diaspora of special-snowflake chat apps and on to better things.