I guess I couldn't explain it when I was on my phone a day or two ago. Let me try again...Lin is sticking her neck out for Tenzin by bringing him in and doing some digging off the records. Korra pretty much knows this now and yet she really shouldn't. Which is going to tick Lin off and make her reconsider helping Tenzin if Korra knows and uses it to sort of pull the rug from under her or Tenzin. That's what I meant. I mean if you were in Lin's position, having a kid overhear something that important and sensitive wouldn't give much reassurance to the situation that still has yet to unfold.
Edit - I also found it unlikely that tenzin and lin couldn't have detected Korra sooner than when tenzin did. -shrugs-
I can't change how I feel about it because I personally don't see merit in Korra knowing what they're up to. Bolin, Mako and Asami already want to get involved, and I assumed they would have invited Korra to approach Lin about it the following day, so her over hearing the plan is in your hands, I'll leave it up to you since you have an idea in mind. I dunno, I don't really care anymore, I just wanna forewarn you that Lin is going to be pretty perturbed just when Korra was starting to get on her good side. That's all. -shrugs and waves hands-