That's strange indeed. I can't observe that in my own snaps, but either way it would be nice to have a UI in the store that would allow the publisher to control more clearly the desired outcome of that combination. Shouldn't be hard.
Something like this might be nice: before there are manual edits in the store UI, the interface would look similar to:
- Summary: The snap building tool
That italic text would be slightly grayed out in the background, implying it's the default. Once the publisher clicks on the text box, it can then be edited:
- Summary: Some new summary| ↻ Reset
The reset button gives a chance for the publisher to go back to the original text. In practice it simply erases the manual edition from the database.
There's of course work involved, but that would be a nice and simple way to combine the two sources.