For the tabbed nick completion on a channel, if you try to use it next to a period, it will not work...For instance:
.Zmo[TAB]
It should be able to work because nicks can't include periods in them anyways. Good luck! ;-)
Should $window($active).w[TAB] complete to $window($active).WYSIWYG`
It should if you use tab, because you wouldn't use tab at all when trying to retrieve something like this.
His point, which you apparently missed, is that tab is normally used to evaluate identifiers. Changing it as you suggest would cause problems when evaluating identifiers with properties.
Then simply make it complete only when the period comes after a space, or when it's the first char of the sentence.
But that would be useful only if the reasons behind this are about not being able to complete nicks followed by the '.' mode char. And I don't know if that really happens.. this is only a guess.