This previous answer shows that BIP34 adds block height as one of the fields in a coinbase transaction of a block. This question is about whether block height is calculated fully independently by each node, or the miner gets to influence it somehow (even by providing a garbled value that'll be considered only temporarily, i.e, before the validation of his supplied height fails).

Concrete questions:

• Does this miner-chosen coinbase block height play any role in the determination of the actual block height when other nodes add this block in the chain?
• Is the coinbase block height value "validated" by other nodes and if yes, where in the source code?
• Is there any other imaginable situation/way a miner could pass a garbled height value and try to confuse other nodes?