Single quote not accepted in wiki names. Ex: Coup d'Etat cannot be a wiki link. Too bad since many French names have a single quote between the article and the name.
Wiki words not accepted in titles (! !! !!! etc)
Wiki words don't work when touching a . , ; : etc. They have to be put between parenthesis
When using 2 tikiwikis simultaneously, the system gets confused in the user recognition
Sometimes urls with separate words, rather than appearing with '+' between each words, appear with a coded space %20. Such urls are not as easy to read as the ones with the '+' between words...
Algeria is missing in the list of countries
When the edit/modify categories is made available to registered users, a second 'Category' link appears in the main menu. The 1st 'categories' link only displays the categories, the 2nd 'Categories' (with a capital C) displays them and let the user edit them. Not a big issue but confusing.