I gave “GitHub Issue” link as a simple motivating example, but it is only one of several various. There are also snippets that are full sentences that I might insert in a larger paragraph, e.g. as part of a reply explaining why a different forum is more appropriate.
I also wouldn’t want every instance of “GitHub Issue” to link to our tracker unconditionally and unpreventably. 95% of the time it’s what is desired, but there are certainly times that people need to talk about GitHub Issues on other trackers, and not being able to prevent a replacement in places where it would be wrong is arguably worse.
Ultimately I just don’t understand the need to force a particular behaviour here, when the post editor already provides all the tools for anyone to to whatever they want or need. Adding in arbitrary out-of-band whitespace only serves to reduce the scope of functionality.