For example misinformation is the only reason why even today there are people who think signatures in a SegWit transaction are "removed" from the blockchain! Or for more than a year people were scared of using the new SegWit addresses since someone kept repeating a buzzword called "anyone-can-spend".
1. nodes not supporting segwit do trim off the weight. its why a block has to have separate txid for the different formats, because otherwise a block validation would glitch, also those nodes not supporting segwit, cant then be used as IBD for other peers as their stripped blocks wont 'compute' if given to a segwit node.
yep segwit nodes which connect to non segwitnodes strip a block to pass it to a non-segwit node. but a non segwit node cant then relay that block to a segwit node as its been stripped
core devs pretend 'its all good' your still part of the network' yet your not, you become less part of the relay/propagation network. so thats why that was mentioned to make people aware they are less involved in the relay/propagation/IBD support of other peers
2. before august 2017 it was said that segwit was soft and that it didnt cause a fork and that its safe to use, the debate explained that people cant just use segwit softly until its actually activated and majority support it..
the end result is that devs decided to not include the key creation/wallet payment code of segwit until a few weeks after activation, rather than include it before activation with the other segwit code to prepare for segwit.. because they accepted the anyonecanspend problem would cause a problem if anyone tried to make a segwit transaction before activation via a hard fork