The person who lets a quiet remark finish can change who feels part of the table.

Group conversation has a volume threshold, and anyone below it drops out without anybody deciding to exclude them. A quiet remark gets started, someone louder begins, and the speaker learns not to try again for the rest of the evening. One person turning towards them and saying go on undoes that in a second. Belonging at a table is settled by these small traffic decisions far more than by who was invited.

Watch for the half-started sentence tonight and hold the space for it. Repeating what a quiet person said, and crediting them by name, gets it back into the room without putting them on the spot.