Run the following with a scale of 1.05

import QtQuick 

Item { 
   width: 200 
   height: 400 


   Text { 
       y: 310 
       text: "I might be misaligned" 
       renderType: Text.NativeRendering 
   } 

The 310 is important, there's certain values that trip up.

The result is:

you can see some glyphs are positioned off.

The relevant line causing this is in qsgdefaultglpyhnode_p.cpp

      qreal y = (qRound(glyphPosition.y() * glyphCacheScaleY) * glyphCacheInverseScaleY) -
                        (c.baseLineY * glyphCacheInverseScaleY) - scaledMargin;

Drop the round here, and it "goes away" though obviously that's not the right fix.