When a wiki space that contains multiple continuous blank lines is opened for editing in Rich Text mode and saved with no changes made – confluence deletes the multiple blank lines irrespective of user intentions (and the same is reported by the "view changes" functionality).

The same does not happen in Wiki Markup mode (blank lines including multiple contigous blank lines are preserved as entered).

All edit modes should behave consistently – either delete multiple blank lines or preserve multiple blank lines (I vote preserve).