FWIW, plwiki already limits thanks for newcomers:

3213         '+plwiki' => [
3214                 // Limit to 3 per day for new users (T169268)
3215                 'thanks-notification' => [
3216                         'newbie' => [ 3, 86400 ],
3217                 ],
3218         ],

Technically speaking, this is a simple configuration change, that falls best within TSP's area of expertise.

I'm not sure rate limits for Thanks is within the scope of Product Safety and Integrity

While I'm less worried about rate limiting for security reasons, I would be very curious whether a limit would make 'thanks' more valuable! This becomes more a research question - but it would be fascinating to see what the (longer term) effect would be to switch some communities to a budget of 'thanks'. This could be related to the number of edits they make (a budget of 10, where every 10 edits refills 1 thanks).
My hypothesis would be that with a budget, if sufficiently communicated, the 'value' of a thanks would go up and it might have a larger positive effect on both the recipient and the sender on retention and activity levels.