Harry missed an opportunity to do good with Lesath. He should have given him orders that would make him behave in a way that might make him happier. Like:
"Acquire friends. Acquire power. Acquire happiness. Try to publicly join a faction, if any will have you, so that you aren't a loner associated with the one Death Eater that even other Death Eaters repudiate, but are instead associated with respectable Slytherins. If Slytherins won't have you because you're worthless as an ally, try moving to Hufflepuff. Note that Neville was willing to defend you from bullies; make him and others like him like you. Publicly repudiate your mother if plausible."
And even more importantly:
"Do not ever try to act on my, the Dark Lord Harry's, behalf, or to help me, without explicit orders from me. Not if you're sure you'd be helping me greatly. Not if you're sure I'd approve afterwards. Not if you're among Death Eaters. Not even if you come face-to-face with your mother. Not if you think I ordered it but you can't be sure because I wasn't talking literally. Not if you get mailed orders from me and you know they're from me because they appear under your pillow while you're sleeping and everybody knows only I can do the impossible. Not ever. If I want you to do something, you'll know."
As it is, my story-pattern-matching is yelling that Harry is going to be exposed by Lesath trying to help him.
Those would all be excellent ideas if Lesath was a perfect Occulemens. As it is, as far as Harry knows Snape may very well be mind-reading as a matter of routine. He's probably get away with claiming to be playing along for the sake of manipulating Lesath, but given the circumstances cannot be blamed for playing it safe.
Update: Discussion has moved on to a new thread.
After 61 chapters of Harry Potter and the Methods of Rationality and 5 discussion threads with over 500 comments each, HPMOR discussion has graduated from the main page and moved into the Less Wrong discussion section (which seems like a more appropriate location). You can post all of your insights, speculation, and, well, discussion about Eliezer Yudkowsky's Harry Potter fanfic here.
Previous threads are available under the harry_potter tag on the main page (or: one, two, three, four, five); this and future threads will be found under the discussion section tag (since there is a separate tag system for the discussion section). See also the author page for (almost) all things HPMOR, and AdeleneDawner's Author's Notes archive for one thing that the author page is missing.
As a reminder, it's useful to indicate at the start of your comment which chapter you are commenting on. Time passes but your comment stays the same.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: