What visible marks on Trump's hand caused concern among online observers?

The concern among online observers regarding visible marks on Trump's hand primarily related to bruises. These bruises were interpreted by some individuals as signs of potential health issues or injury, which naturally raised questions about his overall well-being, especially in the context of his public appearances. When a public figure exhibits unexpected physical signs like bruises, it often leads to speculation and concern among the public and media, particularly if those signs are not readily explained. Other options, such as tattoos, scars, or cuts, while they could also draw attention, do not carry the same immediate implications for health or injury as bruises do.