When adding outlines to text, if you continue to increase the size of the outline then you may start to see see horns or spikes or points on some letters. Here are some examples:
This is not a bug inside of ProPresenter; instead it is a bug that comes from the operating system itself.
When our developers are coding ProPresenter, to provide optimal performance they want ProPresenter to ask the operating system to do as much of the heavy lifting as possible. Rendering text is no exception. For our developers to write (from scratch) all of the code it would take to not just render text, but add effects like outlines and shadows and all of the other great ways that ProPresenter can format text, it would take an inordinate amount of time. And this is not a need that is unique to ProPresenter; many applications could never be written if developers had to "reinvent the wheel" for each individual application.
So when companies like Apple and Microsoft write operating systems, they go ahead and write the code for how to render text, and then they publish what are called APIs for developers to use. With this system, an application like ProPresenter doesn't have to write all of the code for how to render the text, we simply ask the operating system to render the text and the operating system does the heavy lifting.
The downside of this strategy is that if the operating system's code has a bug in it, then that bug will get transferred into our application. The "horns" that show up on outlined letters is a good example of this. Both operating systems (macOS and Windows) struggle to add large outlines onto letters. There are technical reasons for why this happens, but there is no easy "solution" (for our developers or for the developers of the operating system).
The workaround would be to lower the size of the outline (thus reducing the size of the "horns") and/or choose a font that doesn't show the "horns" as much (such as Helvetica Neue in the example above).