Can anyone provide an example of how D templates are overridable by global symbols?

[Siarhei Siamashka via Digitalmars-d-learn]

A quote of Iain Buclaw from 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102765 about GDC 
behaviour:

D semantics for template symbols is that they must be 
overridable - even by normal global symbols.

So in version 11.1, the default linkage for templates was 
switched over to weak, and with that, you can't safely inline 
them without violating ODR.

My (most likely wrong) interpretation of this is that the D 
language standard somehow makes it impossible to make template 
inlining decisions at the compilation stage and this job has to 
be delegated to the linker. And as a result, the use of LTO 
becomes required for generating fast binaries. Another 
implication is that fast incremental rebuilds of optimized 
binaries are likely highly problematic.

So I have two questions:

  1. What is the exact wording of the D language standard on this 
matter?

  2. How would one construct a simple example of a template 
symbol getting successfully overridden by a global symbol?

Thanks!