As I explore EW and try to understand how song and presentation themes are applied, I have some questions regarding text alignment when styles are applied.

I created a test slide, using the Blank theme and Content Only slide format. This theme dictates center alignment as the default alignment for text. The slide featured 4 lines of text:
[list:3dmy08a1]
[*:3dmy08a1]First line: hard left-aligned (clicked the Left Align toolbar button)[/*:m:3dmy08a1]
[*:3dmy08a1]Second line: center-aligned (didn't change the default alignment inherited from the Blank theme)[/*:m:3dmy08a1]
[*:3dmy08a1]Third line: hard right-aligned (clicked the Right Align toolbar button)[/*:m:3dmy08a1]
[*:3dmy08a1]Fourth line: neutral (clicked the Center Align toolbar button, which removed its highlighting — none of the text-align buttons were highlighted, so I thought perhaps EW would not store any alignment for this text.)[/*:m:3dmy08a1][/list:u:3dmy08a1]

I then duplicated the slide and applied a different theme to each duplicate: one theme dictated default left alignment, the next dictated center alignment, and the last dictated right alignment. Here are the results:

[list:3dmy08a1]
[*:3dmy08a1]Text that was hard-formatted in the editor ("Hard left", "Hard right") remained unchanged when a theme was applied. This makes perfect sense — you don't want to lose formatting you manually applied.[/*:m:3dmy08a1]
[*:3dmy08a1]There seems to be no such thing as "no alignment": both the "Hard center" and "Neutral" lines behaved identically.[/*:m:3dmy08a1]
[*:3dmy08a1]These lines were the only ones affected by applying a new theme.[/*:m:3dmy08a1][/list:u:3dmy08a1]

So can we assume that the rule with EW is:

Any property that matches the current theme can be modified when a new theme is applied. Any property manually changed from the theme default will remain unaffected.