Bold is for emphasis, i could use italics if you like, however, I can barely tell things are bolded on Firefox with the darkling background, whereas the italics stands out a lot more. So I have gotten into the habit of using bold for smaller emphasis than italics. Italics has a different shape completely whereas bold only looks a tiny bit brighter. Calling that "shouting" seems excessive since it fact stands out the least of these of all these options for emphasis:
"quotes"
bold
italics
CAPSLOCK
Really there's no dif. between where I've used bold and could have used italics instead. And i don't think bolding a single word in a sentence counts a shouting in context. e.g. where i bold "as intended" or "externalities" in the last page were where you'd normally do something like italics. I mean it would seem weird if you were saying "you're not taking externalities into account" and you interpret the bolding there as a full-bore scream. Spoken language just doesn't flow like that. That's just stressing a single word for emphasis, I never would interpret that to mean shouting. If it was a "screaming" sentence then the flow would put the stresses on words such as "not" and "account".
e.g. "you're not taking externalities into account!". <= now that would be shouting.
The type of emphasis-signifier is, in fact, less important than where the emphasis is applied.