How do I make my message appear in bold, underline and so on?

You can use "forum codes".

Once turned on you can use [b] for bold, [u] for underline and so on.

Why not use STANDARD markup tags (ie HTML) like the rest of the world? Life is too short to learn yet another set of codes that are only used here.

Well, this is exactly what most other forums do.

Rather than letting users put in "straight" HTML, which might be abused (eg. huge headings, relocation to other sites, huge graphics and so on), we provide a subset. They are practically the same as HTML, except you use [i] instead of <i>, basically to remind you that you are not coding in HTML.

For example, ezBoard uses "EzCodes" - read about them at: http://www.ezboard.com/intl/aenglish/help/ezcodes.html

These use the square brackets too.

Here is another example, Snitz forums use "Forum Codes" - (http://forum.snitz.com/) they are basically the same, again you use [b] for bold, and so on.

I am not trying to re-invent a slightly different wheel, this idea is well-established already, and in any case, for most postings, a simple use of a small number of codes will be more than sufficient:

[b] bold
[i] italic
[hr] horizontal rule
[code] monospaced fixed format - for computer code
[mono] monospaced for examples of what to type