There are two ways you can opt your agent out of Porch, without disabling the Porch connection entirely.
From the Agent Edit Screen
In your ISN navigate to Clients/Agents -- Agents -- Agents
Then, find the agent you'd like to opt out and click the pencil icon to the left of their name.
Check the box 'Do not send any emails or SMS messages relating to Porch'
Then hit Save Agent and you're all set!
From the Order Form
When editing your order, navigate to the section where you enter agent data and check the box for their record titled: 'Do not send any emails or SMS messages relating to Porch'.
Continue working in, and save your order as normal.