Is HI a covalent compound or ionic compound?
Yes the compound is covalent!
Here, Hydrogen is an electropositive substance (but it is a non metal) and the Iodine is an electronegative (non metal) element. So, the bond formed between an electropositive (non metal) and a non metal is always not ionic however it seems to be ionic.
The bond between HI is a polar covalent bond. It is because Hydrogen is electropositive in nature in comparison to Iodine. So, the bonding is covalent but it has partial polarity in charges.