Alignment of multiline text HAS changed from V5 to V6.
In V5, when you add a multiline text with the text tool, the lines move upwards from the insertion point, as the default is that the text block insertion point is on the lower left. This is pretty much the standard and also “AutoCAD-compatible” as far as I know.
In V6, when you add a multiline text with the text tool, the lines move downwards from the insertion point, as the default is that the text block insertion point is on the upper left.
This may seem nice for you with your multiline text going downward as you type, but as the default setting is for ALL text blocks, single or multiline, it wreaks havoc with everything else, including imports and exports. It means that the insertion point of a text is wrong in most cases and so when moving things to and from other programs via DWG/DXF, the text vertical alignment changes.
I filed a bug report to have text alignment default restored to bottom left, but it hasn’t been acted upon.