A brief primer on something that's been known to baffle the experienced:
Some newsgroups use "bottom posting" -- you quote the whole thread to date and add your comments at the bottom. In a support newsgroup, this allows a person who comes in late to read just the last post to find out what fixes have already been tried and suggest something new. Some newsgroups use "top posting" -- just like business e-mail, you write your comments, then append the entire thread to date so that people can look up any forgotten points without hunting around for the file copies of the previous letters. I don't read any of the newsgroups that use this convention, so I have no idea what makes it useful on Usenet.
Most newsgroups use "quote and response" posting. This means that you quote *only* the part of the post that you intend to respond to, and write your response under the quote. If you respond to more that one part of the message, you write more than one quote and response -- this is sometimes called "interleaving your remarks", but that sounds rather as though you were expected to quote the *entire* post, which you would do only if the entire post is needed to understand your remarks.
Quote-and-response posting takes a certain amount of skill
-- there's a beginner on another of my newsgroups who is frantically oscillating between quoting too much and quoting nothing; I've made a thirty-day killfile to guarantee that my impatience won't lead me to say something discouraging. (There happen to be plenty of good teachers on that newsgroup, and I should stay out of it.) -- but the effort of learning quote-and-response is worth it, just as the effort of learning to speak distinctly was worth it.
When most of the contributors to a thread have mastered quote and response, it's possible to read for meaning without being distracted by the mechanics of communication.
This newsgroup has light traffic and tends to short threads, so there is considerable tolerance for using whatever style you are accustomed to. Alt.sewing is like the short stretch of one-way road near my house: people who need to drive the other way do, and it doesn't cause trouble because there is almost never anyone else on the road. On some streets in my neighborhood, I walk on the left, ready to step out of the roadway when I see someone coming. On some streets I walk on the right, because I *can't* get out of the way, and want to give the drivers an extra split second to avoid me. On the one-way street, I walk right down the middle!
But even in light-traffic groups like this one, discussions that are conducted in conversational style are much easier to follow.
Note that quote and response isn't an end in itself, but a means to make your posts intelligible. Usenet is an asynchronous medium -- that means that some people may see your response before they see the post you are responding to -- so we quote in order to make our posts intelligible to people who haven't seen the rest of the thread. Even in a synchronous medium, some of your readers will have read the previous post yesterday, and won't remember precisely what it said.
I believe you may be accustomed to Web forums; the two I read present the entire thread on one page every time I log in; this makes it reasonable to write something that makes sense only when displayed directly under the remark that it's a response to, but makes it unreasonable to hold a prolonged conversation. Each time I log in to Live Journal, for example, I have to skim the entire thread again to see whether anyone has responded since the previous time; as a result, I seldom see more than one day of comments on any topic. LJ conversations tend to be the kind you have when passing in a hallway, while Usenet conversations tend to be the kind you have when sitting around with a mug of cocoa in your hand.
speaking of cocoa, chocolate is on topic in nearly every newsgroup
Quoting is the commonest way to make a post intelligible, but you will note that I quoted nothing at all in this post, but instead wrote an entirely independent essay. One can also use indirect quotes or summarize the discussion to date, or use any method that makes it possible for people to understand your post without re-reading the rest of the thread.
Joy Beeson