Is there any option to disable newly available feature @mentiion in outlook 2016
No this isn't possible:
"According to my contact at Microsoft, there is no option to turn off mentions. If you think this would be a good addition, make the suggestion at Outlook 2016 for Windows UserVoice."
This is not possible as of now.
But this is a good thought to disable it, try to vote below link.
April 24, 2020
February 14, 2020
January 02, 2020
September 25, 2018