Hi,
For edit of the original post title/content after 5 days, you may request the mod for that fora to make the correction via the report button for the post. For a minor edit it will be dependent on the mod.
As to your creation of a HOWTO via thread, not the best way. You might consider writing a
tutorial. If so then look at the menu to the right 'Write for LQ' and click the link.
Remember that the LQ reply editor has limited abilities. You can setup WYSIWYG via your LQ UserCP or select the Standard Editor which will provide extra formatting controls.
Pentadactyl plugin for Firefox will provide vim like editing that could be used.
HTH!