How to make part of a word bold in org-mode

Question

How can I make org-mode markup work for a part of a word? For example, I\'d like it to work for cases like this:

=Class=es

and

Answer 1

These days, there is a way to do this (without using quoted HTML tags):

(setcar org-emphasis-regexp-components " \t('\"{[:alpha:]")
(setcar (nthcdr 1 org-emphasis-regexp-components) "[:alpha:]- \t.,:!?;'\")}\\")
(org-set-emph-re 'org-emphasis-regexp-components org-emphasis-regexp-components)

Explanation

The manual says that org-emphasis-regexp-components can be used to

fine tune what characters are allowed before and after the markup characters [...].

It is a list containing five entries. The first entry lists characters that are allowed to immediately precede markup characters, and the second entry lists characters that are allowed to follow markup characters. By default, letters are not included in either one of these entries. So in order to successfully apply formatting to strings immediately preceded or followed by a letter, we have to add [:alpha:] (which matches any letter) to both entries.

This is what the calls to setcar do. The purpose of the third line is to rebuild the regular expression for emphasis based on the modified version of org-emphasis-regexp-components.