Possibly unexpected behaviour from ranged milestones with paragraph styles

The paragraph spacing, etc. in-force at the end of a paragraph are what governs the layout.
I.e. the starting state of a paragraph is irrelevant, only the final state.
This means that a \p that contains a milestone that alters a paragraph style will be affected by that style, even if it is the very last thing in the paragraph. I.e. while the character styling effects are different, in terms of paragraph styling these are equivalent:
\p \zright-s\* [.....] , \p [.....] \zright-s \* [.......] and \p [...............] \zright-s\*

This in turn means that

\p [text]
\zright-s\*
\p I expect just this line to be right
\p And this one.
\zright-e\*

Will not do what the user expects. What will happen is that the preceding paragraph will be set right, along with unless there are \ps added before the milestone start and ends.

A solution to this might be to use futurelet to scan ahead, and if the next non-space item is going to be a paragraph mark, to end the current paragraph before the milestone comes into effect. This could be made more efficient if there was a private/internal parameter defined for the milestone that said whether this milestone caused paragraph changes.