Why I see the revolutions of 1848 as a better comparison has to do with the social and economic changes that were occurring across Europe and the frustration of the population at the lack of change in the governments. I am going to lay out my argument without citation, so I apologize for that at the start.
There had been Republics across Europe pretty much ever since the fall of the Roman Empire but, despite being a dictator, Napoleon spread a republican ideals in the countries he occupied. The ones with less of a democratic history. In addition, countries like Barvaria restructured their social systems to create the ability to conduct mass mobilizations. This led to a population whose lives were changing in a liberal way but whose governmental systems were still autocratic. Using the Davies "J-curve" (yeah, I know, you don't like it) you end up with people with rising expectation that hit a wall. The result is revolution. And not just one, but a series of cascading revolutions across several countries. Pent up anger released. In many cases the result was massive repression, but the mold had been cast. With the constant rise in economic wealth which eventually trickled down to the general population things were going to change.
(A parallel to this is an increase in abstract thinking. I am not going to explain this idea in depth, but it led to the rise of nationalism - a somewhat abstract idea for non-island nations. The reason for my other comment.)
In any case, the parallel between the two situation is the rise in an economic middle class and the increase in the idea of liberalism. Eventually the people demand more and when they don't get it through normal means the result is revolution. Now, only a portion of the population actually are pushing for revolution based on liberalism. Others are along for the ride. If the liberals do not have the majority and if they push for modern democracy too quickly, bypassing republicanism, you end up with countries that elect non-democratic governments.
This is my working hypotenuse
One other thing. As you noted it is now unacceptable to use certain tactics. In 1848 there were very few democracies who were assisting the revolutionaries, or at least looking to punish government's who chose to use repressive tactics. The result was a longer transition to democracy. Today, there are many countries aiding the revolutionaries and expecting Utopian results. But the society has not truly transitioned to liberalism. Democracy comes too quickly. Social change takes time even when pushed. Expect instability for many years to come as each of these societies work things out for themselves.
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