Adder and remover sidenote

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | none

There are cases when you only want either adder or remover, important to know both of them need to be found if any is to work.
Merging emphasized notes

Merged both notes into one, in accordance to discussion feedback.
minor #4253 Adder and remover sidenote (kshishkin)

This PR was merged into the 2.3 branch.

Discussion
----------

Adder and remover sidenote

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | none

There are cases when you only want either adder or remover, important to know both of them need to be found if any is to work.

Commits
-------

59b932d Merging emphasized notes
bdd8325 Adder and remover sidenote