There are two versions of the original Google research paper by Brin and Page written in 1997/8 which describe how the Google index was originally structured. Between the two, there is at least one significant difference.
The papers both describe indexing terms per HTML page and using a bit to describe characteristics of a term such as bold, italics, capitalized, etc. This is known as fancy. One paper describes the value in knowing if a term is fancy or not. However, the other paper also describes that a fancy term does not demonstrate significant search value in ranking. In otherwords, while there is value in knowing if a term is fancy, the reality is that a term being fancy did not improve the search results.
For a period, SEOs grabbed onto the first research paper and went nuts without further research. Soon all the SEO parrots where squawking the benefits of using fancy even justifying with data something that was never true. Silly Wabbits! The problem is, Google never saw the benefit of fancy, not even for semantics, and therefore never implemented any algorithms to boost the value of a fancy term. The exception is capitalization, however, this was only a semantic signal to indicate a proper name, title, company, etc.
So, the short answer is, terms in bold, italics, and capitalization have no value in boosting search results. Period. Never did. Likely never will. Not even semantically. They do have value for a user which brings me to my final point. Create content for your user not machines. SEO is important, but please, do not get into the weeds.