Expression text badly placed by default, placement not saved

Expression text (added via Ctrl+E or from palette via drag/drop or by double-click) gets placed too close to the staff - basically touching it. Press X to flip it above, then again to flip it below, and now it positions how I might expect - same as staff text flipped below.

I guess what is happening is, the expression text is created as staff text with Tid::EXPRESSION and then explicitly set to Placement::BELOW, but it's taking the default offset from EXPRESSION text style, which is 0. I think probably the easy fix is to just pick a more reasonable default offset for the text style - probably the same 3.5sp used for staff text, since that's where it ends up anyhow after two flips. But it's worth considering if we want to make expression text a more "first class" citizen, rather than just a special text style for staff text.