The four built-in ways to create links in Harlowe produce slightly different HTML output depending on which series of (1.x or 2.x) use are using, this can effect the CSS required to style them. So assuming your TwineScript looks something like the following:
''Internal Link Types:''
[[1. Markup based->Second]]
(link-goto: "2. Link-goto macro based", "Second")
(link: "3. Link macro with goto macor based")[(go-to: "Second")]
|link>[4. Named hook with click macro and goto macro based]\
(click: ?link)[(go-to: "Second")]
The 1.x series generates HTML elements like the following for the above links:
<tw-expression type="macro" name="link-goto">
<tw-link tabindex="0" passage-name="Second" data-raw="">1. Markup based</tw-link>
</tw-expression>
<tw-expression type="macro" name="link-goto">
<tw-link tabindex="0" passage-name="Second" data-raw="">2. Link-goto macro based</tw-link>
</tw-expression>
<tw-expression type="macro" name="link"></tw-expression>
<tw-hook>
<tw-link tabindex="0" data-raw="">3. Link macro with goto macor based</tw-link>
</tw-hook>
<tw-enchantment class="link enchantment-link" tabindex="0">
<tw-hook name="link">4. Named hook with click macro and goto macro based</tw-hook>
</tw-enchantment>
<tw-expression type="macro" name="click" class="false"></tw-expression>
<tw-hook></tw-hook>
... as you can see types 1 & 2 produce exactly the same elements and are tw-link based, types 3 & 4 are both tw-hook based but their structures are different, and only type 4 uses the enchantment-link CSS class.
The 2.x series generates HTML elements like the following for the above links:
<tw-expression type="macro" name="link-goto">
<tw-enchantment tabindex="0" class="link enchantment-link">
<tw-link tabindex="0" passage-name="Second" data-raw="">1. Markup based</tw-link>
</tw-enchantment>
</tw-expression>
<tw-expression type="macro" name="link-goto">
<tw-enchantment tabindex="0" class="link enchantment-link">
<tw-link tabindex="0" passage-name="Second" data-raw="">2. Link-goto macro based</tw-link>
</tw-enchantment>
</tw-expression>
<tw-expression type="macro" name="link"></tw-expression>
<tw-hook>
<tw-enchantment tabindex="0" class="link enchantment-link">
<tw-link tabindex="0" data-raw="">3. Link macro with goto macor based</tw-link>
</tw-enchantment>
</tw-hook>
<tw-enchantment tabindex="0" class="link enchantment-link">
<tw-hook name="link">4. Named hook with click macro and goto macro based</tw-hook>
</tw-enchantment>
<tw-expression type="macro" name="click"></tw-expression>
<tw-hook></tw-hook>
... the first thing you will notice is that the structures of the 1,2 & 3 types has changed to now include a tw-enchantment element like that used in the type 4 links, so now all four link types may be effected by CSS targeting the enchantment-link CSS class.
The structure of the type 4 link is currently the same in both series of Harlowe.
You may need to take the relevant HTML structures into consideration when designing the CSS for your story.