the question is the Formality...I have copied-pasted from Tom Lundskær-Nielsen's Grammar: 1 Types of preposition:According to form, there are four types of preposition:(a) Simple prepositions.(b) Compound prepositions:The preposition "i" may be prefixed to four other independent prepositions (blandt, gennem, mellem, mod) to form the compound prepositions: iblandt, igennem, imellem, imod, which are more formal variants of the simple ones.
This sentence has come up twice. The first time I wrote "blandt kattene", and was told I had a typing error, it should be "iblandt". So this time, here, I wrote 'ibland kattene', and was told I had a typing error! Again! I didn't lose a heart either time, but IF 'blandt' and 'iblandt' are interchangable, why tell me I am spelling it wrong??