Everything works fine so far - just poking around in my fresh install of Core 16..... what's this about?? I selected 3rd party drivers on install, since I have Broadcom wifi not familiar with kernel taints.
It can happen if using an unsigned kernel or unsigned modules with a signed kernel.
The signed kernel may be "tainted" by the unsigned one - it is a security warning that if anything is unstable or broken in an unsigned module, this can affect stable and non-broken elements of the signed module or kernel.