Does the angels' supplication for forgiveness and the reward cease if someone sitting in his prayer area stands up to a pillar or a support, or if he speaks with one of the worshippers permissible speech?

The transition of a person sitting in the mosque from his place to another does not interrupt the reward for sitting and remembering Allah Almighty. The intended meaning of "his prayer place" is the mosque in general. If the person sitting speaks about something permissible or something arises that necessitates interrupting the remembrance, this does not harm. In fact, it may be obligatory or recommended to interrupt the remembrance to return a greeting, say "Yarhamukallah" to someone who sneezes, answer the call of the Adhan, and similar actions. Then, one returns to the remembrance after the impediment is removed.