Is the engineer aware of what it is about their communication style that's making others uncomfortable? Even the person most motivated to change won't improve i

Is the engineer aware of what it is about their communication style that's making others uncomfortable? Even the person most motivated to change won't improve if they don't know what constitutes "better" or "worse". There are different communication cultures even within a country or a region. For instance, engineering culture (in many communities or companies) accepts bluntness and directness in ways that the general culture often does not. Or people who grew up on the US coasts are often uncultured to more blunt, direct, fast-paced communication styles than those who grew up in the Midwest or South. Some families treat (friendly) confrontation and debate as a game, whereas others interpret it as conflict or rudeness or even power struggle. If you grow up communicating in one style, you may not be aware that other people use other styles. And even if you are, you may not be aware of how that causes them to interpret your own style. So don't just tell your engineer "change". Give him training in the communication style you expect him to use in the workplace. If you haven't already, I suggest you get some concrete examples from the employees who submitted the complaints. Then spend half an hour to an hour once a week role-playing similar conversations with your engineer. During these sessions, give clear feedback on what comes across as blunt or rude or condescending (and why), and suggest different phrasing or approaches that might be more diplomatic. Keep doing this until you no longer have to suggest significant changes.