The token }} is a bad delimiter for blocks of Lua script code nested in Lean files.
The problem is that the sequence }} occurs very often in Lua code because Lua uses { and } to build tables/lists/arrays.
Here is an example of Lua code that contains the sequence }}
t = {{1, 2}, {2, 3}, {3, 4}}
In Lean, (* ... *) is used to create comments. Thus, (** ... **) code blocks will not affect
valid Lean files. It also looks reasonably good.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>