Consecutive blank lines in some cases control the rendered page, with the risk that less experienced editors write articles so the look is inconsistent across same page or different pages.

The issue was raised here:
https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#Should_spacing_before_heading_depend_on_number_of_blank_lines.3F

With more examples are shown here:
https://en.wikipedia.org/wiki/User:MortenZdk/sandbox#Example_of_spacing_before_heading

Since consecutive blank lines do not have a well defined effect on the rendered page, it would give a more consistent rendering if consecutive blank lines were collapsed.