I don't get the logic of the thread tbh.
It makes sense to western thinking but not through the lens of Russia.
The argument that it will only be used to demonstrate resolve to use and serves no tactical or strategic benefit and can only cause mass casualties of civilians therefore the threshold to use will be very high misses some really key points I fear.
The first point is that the Russians deliberately use terror as a tactic. Much of their bombing and artillery campaign serves no other purpose. Civilians are deliberately targeted for this reason. There is a reason here to try and crack the west by scaring the public and dividing NATO / EU as we have seen just yesterday with the attempt to try and blackmail the Bulgarian with gas. Thats backfired and now the Bulgarians are more determined to send weapons and I suspect it is making the Germans speed up their efforts to find alternatives.
Secondly Putin is under increasing pressure to do something. There are internal calls to show strength in the face of embarrassing loses and uturns. Another significant loss could turn up the dial significantly. The level of this pressure means the bar of an attack in terms of whether its sensible changes; you get a switch from logical reasoning to emotion led reasoning. Its going from acting rational to acting out of frustration and desperation. We aren't there yet (some way to go on this) but as sanctions kick in and fuel embargoes eventually come into force and the backlash over the body count comes in, we don't know where this is headed. The danger is the loss of temper with the situation.
Third the whole point of an existential threat is that if you don't do something you lose everything. You have nothing else to lose. At that point the calculation doesn't need a high threshold, it can be purely vindictive rather than tactical. There is mountains of evidence to suggest that Russia has been motivated by pure vindictiveness at times during this war.
The arguments are nice and soothing, but overlook some of the most important factors here about how the West and Russia aren't understanding each other.
The West constantly applies the logic that no one would do something so terrible because its self destructive not accounting for the level of misjudgement and lack of understanding of the situation and how Russian thinks the west will react to its moves. Russia demonstrates that it thinks it can get leverage by doing something by thinking the west are weak, only to find the we have other ideas.
I am not saying that this means we are doomed to nukes. So don't start panicking. I am saying that if you are failing to add in the above three factors you are not necessarily assessing the situation accurately either.