There is no denying that communication is a vital skill for in-house lawyers and often it gets insufficient attention.
Adopting the technique of talking quietly and diffidently if you are not sure about what you are saying or the reaction it will provoke is less effective than speaking clearly and audibly, if need be qualifying what you are saying. We notice this in workshops. Sometimes a participant will be so softly spoken that one has to strain to hear the comment they are making.
Poor delivery of something which should be heeded does not do it justice.

If you are not confident about expressing yourself, do try to get some coaching on how to increase that confidence. Many years ago I remember being very nervous when called upon unexpectedly to brief a board meeting. It made me realise that this was something I needed to be better at. There is a lot of support available – ranging from books and videos to full presentation skills courses and coaching.

On the other side of the coin, being overly assertive can be a problem. It may be preferable not to interject too rapidly or forcefully in meetings. Often it can be more persuasive to have a quiet word with someone before or after a meeting, rather than making a devastating point at the table.

Although it is a world away from the lives of most in-house lawyers, the revelations at the Chilcot Inquiry about the commissioning and fate of legal opinions as to the legality of war demonstrate how difficult it can be to ensure that legal advice is factored in at the right stage and is not upstaged by apparent imperatives.