This article is from the comp.sys.acorn FAQ, by Paul Vigay with numerous contributions by others.
There are two ways this can happen. The first, and most common way, is when you see two copies of the FAQ, one set posted to comp.sys.acorn.announce and the other set posted to comp.sys.acorn.misc. This occurrence is caused by your news handling software being broken. The FAQ is, if you check the newsgroups line when it is posted, crossposted to both of these groups.
This means it is actually posted just the once and with all good news handling software you will read the post exactly once. Given that this is supposed to be standard behaviour for newsreaders I refuse to stop cross-posting purely because people are seeing the posts twice. Quite simply it isn't my problem and I will need other justification before I stop cross-posting.
The second way it can occur is when you see two copies of the FAQ in the same group. Careful checking of your newsbase should reveal that one copy is about 30 to 32 days older than the other. This comes about because I use the Expires: header to ensure that a copy of the FAQ is always present in all well configured newsbases.