That’s just a normal shortcut for mental math. Break your problem into simpler problems then combine, in this case if one wants to know 7+6 this is being turned from 7+7=14, an easy problem to remember, into (7-1)+7=14-1=13.

That doesn’t feel exactly right as it’s not exactly the way you think about it, but words can’t describe such inferences of thought other than to call them what they are which is not exactly how one’s thoughts reflect them.

Where can I find these “filters” that do this? All I can find are ones that give me massive google eyes and a top hat!

I disagree. The only reason we don’t need the /s here is because this is largely a community of like-minded individuals so we understand when sarcasm etc is in use as it doesn’t align with what we can assume they would believe. This is a dangerous thing. Without anyone to provide new opinions we slowly become more and more comfortable with our more extreme opinions and even more extreme ones become palatable. Additionally no one sees flaws in arguments as everyone just agrees and doesn’t pick at it to find issues. This creates not only an extremist community surrounding Lemmy, but also creates a social stigma surrounding it as human biases promote the extremes in our memory (same principle that many news sites use with outlandish articles). This means we will grow as a platform in an unhealthy way, only taking in new people like us and rejecting anyone who disagrees (even though disagreement is important) as well as slowly drifting towards the extreme ourselves (confirmation bias plays a big role here). This is the same reason big communities of liberals and conservatives have each respectively grown so much farther apart since the rise of the internet allowed them to convene with larger groups of likeminded individuals than in any other period of time in the United States. This sentiment in your post here is a symptom of a larger problem with the fediverse as a whole, even if it seems nice right now. I don’t know what can be done to remedy it.