Why is this transaction referred to as "low fee"? Why does Blockchain.info refer to this transaction as "low fee", when it has the normal fee? What is wrong with it? Its size is less than 1000 bytes, with a fee of 0.1 mBTC – yet, this transaction just got stuck?

Could anyone please explain please what happened and why it got stuck?
It is 1343 bytes, larger than 1000 bytes, so you should have paid 0.2mBTC.

You have too many inputs in this transactions. If you had used a compressed public key, you might be able to save some bytes and shrink the transaction size down to under 1kB.