Meta refresh is discouraged by W3C - 301 is considered best practice for my purposes. I also don't like the part where users can't hit the back button without getting redirected again.
If we all listened to the wc3 ..Google wouldn't have a search page ( and they wouldn't make squillions of dollars yearly ) ,Microsoft wouldn't exist ( and they wouldn't make squillions eithier ) , Apple ..likewise and Pinterest wouldn't exist..
And probably over 75% of the pages on the web wouldn't work..
But they do ..so :)
Pinterest are not about to start listening to anyone about re-directs "spammy or otherwise" if they did they would lose their "plausible deniability" ( "wasn't us was them damn members" ) which is their fallback in all areas for when the brown stuff eventually hits the fan,( on someone with some political clouts desk ) and they catch some ( or some one they know does ) and Pinterest are not able to brib^^^^^lobby their way out of it..
Or until the VCs backing this running IP abusing disaster, have found some mugs to buy it off them, before it falls over, and there is blood on the floor..
Meanwhile..back at the swamp ..meta refresh will get you what you need ..and those who cant get back to the kittens and stilletto lace pron site ..won't be wasting good "pinning time" telling each other about how you killed the back button ..:)
Why worry about the inconveniencing the users on Pinterest ..Pinterest sure don't..they already threw them ( and webmasters ) under the bus with their TOS ..
Their "flaky" "we're so busy" "chair spinning" "support" is an act ..they know damn well what they are doing ..appearing to be a bunch of ditzes is an old old way to be left to scam, and wait for the marks to come and buy the thing, and then one can go count the money in peace..and they can always blame the, we "we''re so busy and "the ditzes", if challenged ..
Hey ..works for Google with youtube :) ..they only do "take downs" for Governments that might take away their freedom, or their heads if they ( Larry and Sergey and the "higher ups" ) went there on Holiday ..