A reader adds:

It is unbefuckinglievable that someone would say unfuckingbelievable. The stress test is tautological, it isn't just that the stress follows where fucking would normally be inserted, it is that fucking SHOULD always be inserted prior to the stress. It is a phonetic necessity for the use of fucking to have its full impact.

Another explains:

Obviously your reader isn't familiar with the "except after 'un-'" exception to the Fucking Stress Test. Drop prefixes before applying the test.

I guess if I haven't yet been blocked from most expletive-leery sites, I am now.