Hey Julie, I’ve actually solved this by writing the following guidelines based on the replies to this question:
Liking is a “thumbs up” 
feature in Asana (top left corner in the task or next to each comment).
We can use it in two ways:
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To show that you accept a task assigned to you, that you have seen it and that you’re ok with the description and the due date.
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To approve something. For example, I can say " @Sofia are you ok with us to contact them?" Rather than replying I can “like” the task. Or I can ask "I’d like @Sofia 's approval on this while tagging me using the at sign. I can now like this comment as approval of that particular task.
When NOT to use likes:
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As a thank you - it clogs the inbox, especially during the busy times and
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Like we use it in teams to show our support for something - if you have something to say, you can comment in the task.
If you’d like to celebrate an achievement within a task or a conversation, you can use Celebrations (bottom left - an icon with a star) Appreciations: a new way to celebrate and encourage your teammates in Asana - see my example below.