IFTTT indeed prevents recipes from posting the @ sign. I believe this is a condition set by twitter to prevent IFTTT from spamming users.
The way around this is in fact using two separate IFTTT recipes:
- Twitter to Google Sheets: use this recipe as Trigger to collect all the info you need like
username
, text
etc... and assemble this info to compose the exact wording of the tweets you wish to send in a dedicated cell.
- Google Sheets to Twitter: use this recipe as Action, to post the content of the dedicated cell to Twitter.
Posting from Google Sheets should resolve the problem.