If I make a comment in an exceptional case, I always add a solution. For example, I place a corresponding resource in the profile and some links explaining how and why and where to find it. In principle I only do this, in my own language, for Dutch members in Dutch so that I can find the right tone, positive, understanding, free of obligation and ... well, don't worry, that's how I started. This is much less successful if, for example, an English-speaking mentor tries to convey his or her message in Dutch via Google Translate. Google Translate translates words and phrases but cannot convey a feeling. For example, the word you is translated as u/uw form (formal) instead of je/jij (informal). This only applies to Dutch, in Flemish the language feeling is slightly different.
I place the comment directly on a relevant profile and if it concerns a problem for the entire family tree, a comment on the profile of the manager. So right at the source. I don't send a private e-mail because it can come across as intrusive and is often not appreciated. I only use private e-mail with members I know better to work together when extensive consultation is required.