I think this will always depend on the particular facts (and obviously I'm not offering advice here). But if it's a private conversation between members of the bar and your friend already knows you acted for someone in such and such matter, which is public knowledge in any event, and all he's asking for is general guidance, then I don't think it would be unusual to discuss what kinds of things the court was looking for, what worked and what didn't, things to avoid, etc. You wouldn't disclose the reason why you did or didn't appeal or anything that would reveal the content of privileged conversations. But giving general guidance to a colleague to better the expertise of the bar is, I think, different from disclosing to a non-lawyer or the public and since you're the lawyer it's your own ass on the line (rather than an employee risking your ass for you by their own indiscretion).
That said, I don't know that I'm often in that precise situation. Normally, if I'm discussing with a friend about a case in the way you mention, it's without knowledge or disclosure of names or other identifying information.
I had an unfortunate first year in law that ended with a C- in contracts, C in Crim and a C+ in Torts. These grades were not at all reflective of my ability in law school as I had had both a death in the family [missing an entire month, but unable to afford to drop out and start again] and then had on my of children injured in a life altering way a couple months before exams [so not only were exams not a priority - i had no intention of continuing with law].
I took a year off and came back and received nothing below a B my second year [2 A- and 3 As, as well].
I am entering my third year now and have not applied for any jobs as I recognize how dismal my first years grades look - and was both embarrassed and unable to maintain my composure in explaining the circumstance.
Hoping to receive some input from current lawyers or articling students on how they would address this situation or if i should just focus hard on third year and see how things land once the degree is done. I have networked extensively throughout these years, however, I haven't shared my terrible 1L performance or the life-altering events that led to it.