Hiya Higgy...

feel free to rant BUT...leave out persuasive comments like "only a fool..."; there are valid resons not to change filters if you change fuel system components...like the injector or regulator - which is down-stream of the filter, anyway...

in the post he says he's changed the fuel filter several times...that's just unnecessary expense.
if the fuel flows at any reasonable rate it won't be "blocked" to the extent the engine will starve.

if the bike will run at "full gas" or even run well for 20 minutes then misfire...then clean up again (and most will accelerate well, too) the issue can't be a filter blockage..it doesn't make sense.

sure the filters are relatively cheap - but they're in a prick of a place inside the tank; they take at least 1/2 an hour to change out...if you're paying a workshop to do that work they're not so cheap after all...[as a side note - I moved my filter outside the tank to make it easier to replace and check pressure/flow...

it's not so bad if he's doing the work in his own back yard as "trial and error" but if he's PAYING a mechanic for parts and labour to swap out several filters to troubleshoot a misfire on a bike that otherwise runs well fairly simply he's not going to the right mechanic.
In any case - if the mechanic was worth his salt he'd have back-flushed the filter to see what the blockage grit was...

I have been down the track with an undiagnosed misfire; replacing "could be" problem components to trace the fault...you end up spending heaps on parts that were serviceable and hours of labour (either my own or some expensive Ducati tech)...so I guess I wrote the "forget the filters..." in case they were intending to continue with half-assed diagnostics...

cheers mate!