There's been a argument, since the 18th century, over whether than is a conjunction or a preposition or both. Most prescriptivists who write books nowadays say it is only a conjunction, and so is always followed by a clause, even if the clause is often missing some words:
You are wiser than I [am].
You love him more than [you love] me.
But it's been a preposition since the 16th century, and can be followed by object pronouns or reflexives. The prescriptivist who insists that than is only a conjunction must conclude that these examples are wrong:
A man no mightier than thyself or me
In personal action, yet prodigious grown
And fearful, as these strange eruptions are.
- Shakespeare, Julius Caesar
And, though by Heaven's severe Decree
She suffers hourly more than me...
Swift, To Stella, Visiting Me in Sickness