What you see in the MText entities is an AutoCAD feature, which puts formatting information into the text field.
In AutoCAD the formatting info is extracted and applied to the text for individual formatting.
LibreCAD does not support this feature, thus you have the full content displayed.
Sadly, there is no other way yet than removing the formatting one by one.
We are aware of this feature, there are already discussions here and on GitHub, but nobody has set hands on it yet.
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