When one customizes the WikiEditor toolbar, adding a button according to the [[https://www.mediawiki.org/wiki/Extension:WikiEditor/Toolbar_customization#Add_a_button_to_an_existing_toolbar_group|docs]], the new added buttons behave differently than the existing buttons.
They have different DOM structures:
{F35316034}
And in some cases (e.g. changed default browser font size) it results in them having different sizes and misaligned highlighting:
{F35316040}
The reason for the last is that the custom buttons use fixed sizes (`32px`) while the native OOUI buttons use sizes relative to the current font size (`2.14285714em`).
I currently fix this in #convenient-discussions with this rule:
```
.cd-commentForm .tool-button {
width: 2.14285714em;
height: 2.14285714em;
border: 1px solid transparent;
}
```