Clarity 1 can't be socketed in 2 different skills "Your character is already using this support gem"

Non-lineage Supports aren't limited to 1 per character anymore.

Their category means you can't have multiple of the same category in one skill.

You can correctly equip Clarity 1 and Clarity 2 in two different skills.

You can't equip Clarity 1 and Clarity 1 in two different skills.

Spirit-reserving supports are limited to 1 across all skills, though it doesn't explicitly state this on the gem.