The game writes a large number of debug messages like this:

DebugOutput: Ping: 1.59673ms

Suppress those messages unless SMAPI is in verbose mode.

One debug message that SMAPI may also want to filter out is of the form

DebugOutput: playerPos: {X:433 Y:622}, mousePos: 292, 379

This gets written to the console every update tick that the player's mouse moves when they're aiming with a slingshot.

Both done in develop for the next SMAPI 2.6 beta.