general truth vs habitual acts

[keannu]

This is definitely habitual act in conditional0, but my student asked me if it's general truth. First, I laughed in mind but I couldn't explain for sure the difference, General truths and habitual acts are all factual conditionals based on facts, so they seem similar. But I thought general truths are more like scientific facts(When you heat ice, it will melt), but they also seem plain facts. What can be the standard to tell the two?
And for habitual acts, I don't think it has to be only one person's repetitive actions, but any repeated actions by various people. Right?

ex)Do you write your name in red ink? You probably don't because you have heard the superstition about writing names in red. It says that a person whose name is written in red will die soon. ....There is an origin to the superstition. Long ago in East Asia, red was the color of kings. Only kings could write their names in red. So if ordinary people wrote their names in red, it seemed as though they were acting like kings. The punishment for that was death....

[5jj]

. But I thought general truths are more like scientific facts (When you heat ice, it will melt), but they also seem plain facts What can be the standard to tell the two? [...] So if ordinary people wrote their names in red, it seemed as though they were acting like kings. The punishment for that was death....

The 'standard' is, yet again, CONTEXT.

In the sentence I have coloured green, the scientific truth is a fact.

In the sentence that I have coloured red, 'if' has a meaning similar to 'when(ever).' with the added idea that the speaker is allowing for the fact that people did not write their names in red; the hypothertical possibility is allowed.

As I have said several times before, labels are useful only in that they are a shorthand method of giving explanations. Labels are rarely 100% leakproof.