Regarding I. 33. 2, Bigg’s edition of Books I and II (Longmans, 1896) comments (translating Krueger):
‘One might have expected λυπηροτέρα ἢ εἰ. But, as it would be quite correct to say, εἰ αὕτη (ἥ δύναμις) πάρεστιν αὐτεπάγγελτος, τίς εὐπραξία σπανιωτέρα; so ἢ is absent sometimes even when the comparative comes first’. A parallel from Euripides, Alcestis 879, is then quoted.
My own translation of I. 33. 2 runs:
‘And consider: what good fortune could be rarer, or more grievous to your enemies, than if that very power, which you would have valued more than a great deal of money and gratitude to gain, is available of its own free will, offering itself without danger or expense, …’
John
PS - on Saturday morning I submitted a lengthy post offering some suggestions for Thucydidean study aids, but due to the vagaries of the posting system it has only just appeared; if anyone is interested, it is to be found on page 3 of this thread. Fortunately (and with thanks to those concerned) I can now post in real time!