OK, you've been involved in a lively messageboard conversation when some unmentionable piece of humanity posts the kind of insult at you that hits the synapse marked 'offence'. You have been very publicly humiliated in front of everyone. So what do you do? Your stress meter's rising and you sense you need a quick response. There's no time to hunt through the thesaurus for the right sort of reply; indeed, anything you can think off the top of your head would only be blocked by the site's profanity filter. There's only one retort that will do, and that response is </UNSUB>.
What are you Trying to Say?
When you post </UNSUB>, you feel insulted, you have had enough, and you have decided to leave in a fit of pique. You can put it at the end of a long, defensive, point-by-point rebuttal of all the offensive content, but you can use it to greater effect by just submitting it as a one-word posting, indicating speechlessness. Don't be tempted to add cross-looking smileys - these only serve to lessen the impact.
Of course, there are other reasons you may want to signal your termination. Perhaps you have grown bored of the conversation - and if so, then you should use a less emotive, lower-case substitute - <unsubscribe> is ideal. People will know not to contact you via that message in the future. </UNSUB>, on the other hand, goes a lot further - it is the messageboard equivalent of slamming the door on your way out. It goes without saying that you will neither read nor post to the same conversation again.
Having said this, it is suspected that many unsubbers will go back and lurk to see what the effect was, but there are two very good reasons why you shouldn't do this. First, you may find that your dramatic exit hasn't had the desired effect. Maybe people have added comments like 'ooOOoo' and posted handbag smileys, or maybe everybody has sided with the offending party, and these can only multiply your injury. Second, if you do this, you may be tempted to rejoin the conversation. Be warned - you would suffer a serious loss of credibility if you were to re-post and hence resubscribe. For maximum effect, use </UNSUB> only as a last resort. If you're not sure, then just unsubscribe quietly without posting to say so.
Why the Angle Brackets?
The syntax of </UNSUB> derives from HTML1, where plain text is formatted by placing it within 'tags' - those instructions written inside angle brackets. Those of you who have used Guide-ML on your Personal Spaces or have written guide entries will be familiar with all of this. An example is 'This text is in <B>bold</B> type.' (This text is in bold type.) The <B>...</B> tags indicate that the text within them will be displayed in bold when it is interpreted by an HTML browser.
</UNSUB> itself isn't really a tag in HTML - the style has been borrowed because many messageboard readers are familiar with the syntax and understand that it's supplemental to the conversation - plus, the user may want to fool others into thinking they are savvy with the latest developments in HTML and its extended successors like XML2. In fact you'll often spot this sort of 'faux-XML' construction within messages; off-topic items could be placed within false <aside> ... </aside> tags, for example.
Why the Slash?
The slash which precedes the word UNSUB is actually tautological, or redundant. A more logical tag would be </SUB>, but this has another meaning in HTML - it's the closing tag for text in subscript, as in 'The formula for water is H<SUB>2</SUB>O.' (The formula for water is H2O.)
Alternatively, we could write <UNSUB>, without the slash, but HTML parsers would insist on this having a closing tag3 - <UNSUB> would need to be followed by a </UNSUB>.
Perhaps the answer is to post a simple <UNSUB/> with the slash at the end - it's the syntax used in some self-closing tags, an example being <BR/> - the tag which adds a line break to your HTML document.
Looking Cool When You're Mad
So there you have it. The next time you decide to storm out of your conversation, remember to put that slash at the end of <UNSUB/> - you will earn just that little bit more respect amongst the XHTML-programming crowd.
For more information on Netiquette in general, take a look at this introduction to the subject.