Misquoting the Mishna Berurah is more offensive than davening in Crocs. Again, the MB does NOT say that ONE MUST DAVEN WITH A JACKET as some claim.
Hakol Lefi Minhag Hamakom. When I lived in Brazil and nobody OWNED jackets (politicians went around in shirtsleeves) would you say that every single tefilla was in violation of your warped reading of the MB?
The Mechaber has a list of things that if done or not done invalidate a tefilla. Not wearing a hat or jacket is not on that list.
Reading the halachos, one can reasonably say that it is better to daven wearing neat and clean casual business attire (shirt and pants) and not an untucked white shirt with 2 coffee stains, a jacket haphazzardly thrown over the shoulders missing 2 buttons and an old dusty hat tilted precariously on the back of the head. Of course, there are those who will argue, but, they have a hat and jacket, thats all that matters.