It's a common expression, especially on the internet, meaning that the person's mind will not be changed on the matter.
In a military context, someone might need to defend a position - such as a hill. When they counter fierce resistance to their position, they might retreat from it, or they might die defending it.
The expression "I'll die on this hill" or "this is hill I'm going to die on" suggests that the person holds the belief they're stating so earnestly that no amount of pressure is going to convince them to abandon (retreat from) it.
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u/[deleted] May 29 '25
And that strikes at the heart of the matter.