At the moment, when you post a new topic on a Talk page (or when replying to an existing topic), we don't show a preview of the resulting text, and instead just post it immediately. This can be a bit jarring and unexpected, especially since we're now expanding the kinds of wikitext markup (templates etc) that can be included in a talk message.
This task is to introduce a Preview screen, identical to the screen we use in the general Editing activity, so that the user gets a chance to see their message as it will be formatted upon posting.
Note that this will be a WebView-based preview (same as in the general editor), so the appearance of the previewed message may be slightly different from how it appears in the native Talk screen.