To be short- the majority of seats were not very comfortable.

In the Dury Lane Theatre of 1794 the pit could hold 800 spectators. There were 25 rows of wooden benches which filled an area 55 feet deep and 46 feet wide. There was no middle aisle. The only London theatre that had middle or side aisles was the King’s theatre.

Each bench could (it has been estimated by the Theatre Museum) accommodate 32 people.

In “A Treatise on the Theatres”(1790) George Saunders remarked;

The public should not submit to be crowded into such narrow seats: 1 foot 9 inches is the whole space here allowed for seat and void

Remarkably, this is the only dissenting voice that I have found remarking on the conditions endured by spectators at these theatres.

It seems that most ordinary theatregoers simply put up with these conditions, knowing no other. (Save for the chap who appealed so endearingly to Mrs Jordan when he was being squashed in the pit!)

In the boxes, the seats in the front rows were furnished with separate chairs. But only in the Royal Box would it be furnished with chairs throughout.

The back rows of the boxes and in all the galleries had only benches-again wooden.

All these benches were covered by baize -which may explain the need for some of the green bias used by Mrs Norris in Mansfield Park! - but none of the benches , even those in the boxes , had backs. This would make them rather uncomfortable for use, IMHO.

The first commercial theatre to provide backs to the pit benches was the Haymarket in 1843!

You might be interested in the different types of boxes in these theatres.

Side boxes extended along both sides of the auditorium.
Front boxes were actually situated at the rear of the auditorium but directly faced or “fronted” the stage, affording a good view.

Stage boxes were on the forestage itself directly in front of the proscenium arch.

The Royal box was always next to the proscenium arch, on the audience’s left hand side. It was always decorated when there was a command performance and the Royal family was due to attend. If they were not coming to the theatre however, it was available to the general public. for their use.

Private boxes were at the stage ends of the first gallery.

You might be concerned for the occupiers of the lower boxes; could they see over the heads of the "standees" in the pit?

Well, yes they could, because they actually stood in a shallow trough, which encircled the pit. It was, to quote from the Public Advertiser of 25th September 1782;

“A step lower then the floor on which the benches are placed”.

The pit was "raked" also; therefore no standee would impede the view of the occupiers of the front or side boxes.