opinions, I wonder what their behaviour looked like;

"...their behaviour, at all times, was an illustration of their opinions."

If 'absolute' was their opinion then I shudder to think the discomfort caused by them by their behaviour expressing it, to at least Elinor.

Not Mrs. Dashwood though, who;
"...entered into all their feelings with a warmth which left her no inclination for checking this excessive display of them. To her it was but the natural consequence of a strong affection in a young and ardent mind."