It seems that the maximum block size is set to 1MB:
// BlockSizeLimit specifies the maximum size an imported block can have.
var BlockSizeLimit = 1048576 // 1 MB
(1) why 1MB? It seems that this value was once 2MB
(2) the limit is part of
unixfs. What happens if a larger chunk is added with a lower level interface (e.g.
ipfs dag add)?