since the fibers ARE spliced together---yes, it is common-
with Cotton Thread. it is the manufacturing process.
the long staple egyption threads - the slubs should be an inch or two apart.
some threads it is more evident than others, but it is pretty much always there==
poly threads and some other are made from continuous fibers- cotton the fibers are short (couple inches max) and are spun together.
superior threads has good free (choosing the right threads) information on their web site- will answer alot of questions.