I do find even outside-the-standard CL libraries somewhat more portable than Scheme libraries. Varies by library, but CL library authors seem to make more of an

I do find even outside-the-standard CL libraries somewhat more portable than Scheme libraries. Varies by library, but CL library authors seem to make more of an effort to test on multiple implementations, using conditional compilation where necessary. It's semi-standard to use a compatibility layer for extensions, e.g. use Bordeaux-Threads rather than directly using sb-thread. Whereas Scheme programming style (at least in the Chicken and Racket ecosystems, the two I've used) seems to make more direct use of implementation-specific functions and comes with less expectation that any nontrivial program will run on another implementation without porting. At least that's the case in the newer "open" CL world; older CL code, especially commercial code, more often did target a specific implementation like Franz, which is more like the Scheme approach.