[QGIS-Developer] how compatible .qml files are ?

[Sandro Santilli]

I just filed https://github.com/qgis/QGIS/issues/31471 after finding
out that a .qml file created with QGIS 1.9.0 is not fully honoured
with curretn QGIS master (and I think 3.4.0 as well).

Yes, I know 1.9.0 is old but... is this level of backward
compatibility supposed to work ? Or are there tools to convert
saved styles across versions ?

--strk;