\par, TeX is in vertical mode. Then page 283 of the TeXbook, second bullet, explains that
\par command has no effect when TeX is in vertical mode,
except that the page builder is exercised in case something is present
on the contribution list, and the paragraph shape parameters are cleared.
“Exercising the page builder” is explained on page 281:
TeX periodically takes material that has been put on the main vertical list and moves it from the “contribution list” to the “current page.” At such times the output routine might be invoked. We shall say that TeX exercises the page builder whenever it tries to empty the current contribution list. The concept of contribution list exists only in the outermost vertical mode, so nothing happens when TeX exercises the page builder in internal vertical mode.
The paragraph shape parameters are any value given to
So no, you don't have to worry much about having consecutive
\par tokens unless you have redefined
\par. Two consecutive blank lines count for two
\par tokens, as the following Plain TeX example shows: