BuddyPress.org

well, you can ,but it is hardcoded in the bp-activity/bp-activity-templatetags.php

Open this file

and take a look at the function

bp_activity_template

You will see something there

like

$this->pag_links = paginate_links( array(

'base' => add_query_arg( 'acpage', '%#%' ),

'format' => '',

'total' => ceil( (int)$this->total_activity_count / (int)$this->pag_num ),

'current' => (int)$this->pag_page,

'prev_text' => '«',

'next_text' => '»',

'mid_size' => 1

));

Change the mid_size value from 1 to what ever you want.

Hope it helps.