• Ignore it
• Downvote it
• Reply and correct it
• Send the poster a message with a correction

Two of those give *useful* feedback to the poster. A downvote doesn't -- it's a one-bit message that doesn't communicate very much. Posting a followup allows for more room to explore and to explain the reason why it's wrong. Also, it'll enter the archives forever attached to its parent.

Sending a message works in cases where the poster just missed the boat and presumably knows better. People misread questions. It happens.

Now the poster of an incorrect node also has several options:

• Ignore it
• Reply to it
• Censor it
• Update it

Two of those leave useful information in the database. One of those potentially notifies the user who posted the original question.

In my opinion, it's better to reply, whether by writeup or message, to an incorrect post. This gives the poster the chance to correct it (if by /msg) or attaches a correct answer to an incorrect answer. A downvote doesn't accomplish much, but it has the chance of attracting the poster's attention to possibly incorrect data. It doesn't tell what's incorrect, though, and it doesn't put any data in the archive, though it may prevent an incorrect node from sticking around.

Far better to be explicit. If it's wrong, explain why it's wrong. Give people a chance to correct it.