How to style text within locize?

You may be trying to do some basic stylization: bold, italics, underline, etc... Ideally, you also want to add links within a string as well (i.e. a html tag)?

Styling translations depends less on the string - but on the technology (and i18n format) used to render content.

For react-i18next for example, you can use simple HTML elements like <br /> and others:

<Trans i18nKey="welcomeUser">
  Hello <strong>{{name}}</strong>. <Link to="/inbox">See my profile</Link>
</Trans>
// JSON -> "welcomeUser": "Hello <strong>{{name}}</strong>. <1>See my profile</1>"

<Trans i18nKey="multiline">
  Some newlines <br/> would be <br/> fine
</Trans>
// JSON -> "multiline": "Some newlines <br/> would be <br/> fine"

For locizify, you might use different content on merged elements (there might be limitations):

<p merge>
  all inside will be used as on segment, even if having other
  <a>elements inside</a>
</p>

// key = all inside will be used as on segment, even if having other
<a>elements inside</a>

For plain HTML, you will have to append the translation to the html element as innerContent.

So, really depends on where the string gets rendered and with what technology.