What I don't know is the reason for the fascination with probing the mains voltage.
Listen, asking if I can measure mains voltage is my way to ask if I can measure hundreds of volts of anything with the oscilloscope (assuming that voltage is below probe & oscilloscope limits). It's not like I feel fascination for mains.
Mains is a different beast when compared to, say, a local high voltage power source whose characteristics such as maximum voltage/current and source impedance are well known.
Mains has a low impedance that can yield currents at the order of kA as mentioned by rstofer, which will be only relevant if a breakdown or an arc happens between the power source and the test equipment (oscilloscope, probes, etc.). The chances of such event occur are defined by either a transient or an accidental mistake.
A transient is extremely hard to predict and can reach spikes at the order of kV which can easily exceed the probe safety specifications. Given the very low impedance of the source, any arc will be quite an event.
Accidental mistakes can be (but not limited to) either shorting the probes or inadvertently switching the probes from 10:1 to 1:1 (several regular oscilloscope probes have this tiny switch on them).
Probing a high voltage power supply is different than mains, given the fact that, even if it has a similar impedance as mains, it still has an advantage as spikes may not exist or be well characterized - thus eliminating the element of surprise.
All in all, kudos to you to double-check your procedure on this forum. In a very distant past I measured the voltage of the three-phase 60A bus bars feeders to my house and no surprises happened, but I was ignorant of all these factors at the time and did not take any precaution other than checking the maximum voltages of the 10:1 probes.