Hey! Yep, you're not missing anything — Zapier can definitely do this, but with a small catch.
Airtable doesn’t treat comments as a trigger in Zapier by default. One workaround is to use a separate "Comments" field in the record and trigger the Zap when that field gets updated. Then, you can send that value to Linear using the “Create Comment” action.
It’s not the exact native comment thread, but it gets the job done. Let me know if you want help setting that up!
Hey @TodoCartões Tech, welcome to the Community! 
How did you get on with the approach Adil Waqas suggested. Did that work for your needs here?
If not, it looks like it’s possible to enable email notifications for comments in Airtable. So as a alternative approach, perhaps you could forward those email notifications to an app like Email Parser. Email Parser would then extract the relevant information from the email pass it over to Linear. You can learn more about how to work with Email Parser here: Trigger Zaps from new parsed emails.
Look forward to hearing from you!