Yes, styled text drawing builds upon the text formatter we developed for the fit-polygon styles. The tsFitPoly styles are multi-line too, e.g. this displays two lines:

b1.Style = bsShape
b1.Shape = fcx.Shapes("Decision")
b1.TextStyle = tsFitPolyCenter
b1.EnableStyledText = True
b1.Text = "<u>line 1</u>" + vbNewLine + "<b>line 2</b>" 

I hope that helps,
Stoyan

The control does break long lines of styled text, but I think it does that only at white-space symbols. You might have to add new-line or space symbols if you want to display some long sequences that do not include white space.

Perhaps for historic reasons; they were there much before the FitPoly styles. Also the ML styles correspond to a single call to the DrawText Windows API function, while the FitPoly formatter parses strings, lays them out inside the shapes geometry, etc. So the ML styles are more lightweight and you might prefer them if the diagram contains much text. Also the ML styles let you align text horizontally, while the poly styles are always centered.