First of all, bear in mind that each Wiki Web has a purpose. To a large extent, the purpose is defined by the users. However, if the user base (or the administrator) has already chosen a purpose for this Wiki, and if what you want to say has no relevance to that topic / does not advance that purpose, then you still have a right to say it, but you are probably saying it in the wrong place.
Sometimes ideas on a Wiki generate lively discussion, just like they do on a newsgroup. This is a good thing: discussion / debate can lead to a synthesis of differing opinions, or sometimes the differences are the interesting thing about it. The Wiki supports this kind of lively discussion; you simply edit the page by adding to the bottom (with a
---- bar to separate your text from the previous text), and Sign Your Name. If you find that a page is generating some interesting debates, you may want to add a reference the Discussions.
Like Doplhin Wiki, Spinner Wiki can accept many of the common HTML tags as part of the Wiki Text Formatting Rules. However, try not to use too much HTML since this will make pages difficult to edit. Use of the HTML heading tags is a good idea and, for consistency, I would suggest making H2 the top-level heading within a page (one can consider the page title as being an effective H1 heading).
Finally, if you write in the first person then be sure to Sign Your Name after your piece.
Further Wiki style tips
If you like, you can also read WardCunningham's original tips on Good Style.
Related pages: Wiki Beginners Topics