The Ars Magica FAQ at http://www.redcap.org/FAQ/FAQ.html has been updated for Fifth Edition. I recently took over as FAQ maintainer.

The FAQ is unofficial and it may contain errors, though David Chart has seen it and didn't raise any objections. I tried to capture most of the Fifth Edition questions that are actually being asked frequently. If you think I've missed something, please let me know.

I would be glad to answer new questions. Either post them here or e-mail the FAQ maintainer. If you happen to provide answers to the questions, that increases the chance they'll get added to the FAQ (copy and paste and then a light edit is easier than writing a whole answer myself). Please give your name if you want authorship credit for your FAQ entry.

We now return you to your regularly scheduled Ars Magica discussion.

ERRATA:
Puissant (Ability) (p. 48): Replace the first sentence of the text with: "You are particularly adept with one Ability, and add 2 to its value whenever you use it. Note that you do not, in general, use an Ability when learning it, teaching it, or writing about it."

FAQ:
Does the Puissant Ability Virtue affect what the character can teach and write? Does Puissant Magic Theory let a character use more vis in the lab?

The errata make this more clear. A character with Puissant Ability treats that Ability as if it were two points higher for all purposes, including teaching, writing books, and using vis in the lab.

Thanks, this will be fixed in the next update.

Actually, I shouldn't have said "thanks." You need to be more polite.

What exactly did I say that was impolite? I cut and pasted two chunks of text. There was no editorializing, only a strict quotation.

Should I have apologized for noticing the error? Please tell me how I should have made my post "polite."

It's easy on these boards to read sarcasm or mean spirit into something that is written. There are no body language clues or intonation to tip us off, the way there is in normal conversation. That doesn't mean that it's actually there. Maybe you shouldn't jump to the conclusion that someone is being mean without a little more evidence.

As an aside, I would never be mean to someone who provides the incredibly valuable service that your FAQ does. It saves me a huge amount of time, so I don't have to explain every confusing concept in the book to my players.

What ruffled my feathers was that you pointed out the error with no preamble whatsoever -- it seemed very blunt. A few words to the effect of, "I found something that looks like an error" or "I'd like to help out, it looks like you missed something" would have been plenty.
I don't think you need to apologize for being right: just to give a little introduction that shows you're trying to be constructive. Without that, as you say, who can tell how your comment was intended. People rarely like to hear bad news, so I think pointing out someone else's mistake does deserve carefully-chosen words.

At first I shrugged it off but then later it kind of bothered me, so I figured I'd say something rather than just be quietly irritated. It's now clear you didn't mean to give offense.

Thank you for your kind words about the FAQ. It really pleases me to hear you found it useful. :-)