They may speak from the side galleries, but due to the lack of microphones there is a strong disincentive from doing so. Also, the Speaker will not call a Member in the Gallery if there is room downstairs. They must stand whilst speaking, but a disabled or incapacitated Member is naturally allowed to address the House seated. The style of debate in the House has traditionally been based one of cut-and-thrust; listening to other Members' speeches and intervening in them in spontaneous reaction to opponents' views. It is thus very different from the debating style in use in some overseas legislatures, where reading of set-piece speeches from a podium or from individual desks is much more often the norm.

I watched a bit of C-SPAN coverage the other night. it seems that they now accommodate the back-benchers with overhanging microphones. the front benchers may not give set-piece speeches, but they have enormous 3-ring binders full of notes, which they carry back-and-forth to their small podium adjacent to the speaker's desk.