The ability of normal people to follow a fight between characters moving at subsonic speeds or higher is not necessarily an anti-feat. It largely depends on the context of the story and the way the fight is portrayed.
- They might use various techniques, such as slow-motion, clear choreography, or special effects, to make fast-paced fights visually comprehensible to the audience.
However, if a story explicitly establishes that characters are moving at speeds beyond what the human eye can perceive or comprehend, and normal people within that story can still follow the fight without any explanation, it could be seen as a lack of consistency or attention to detail on the part of the creators.