# Block-comment delimiters are configurable strings, not a fixed `#|`/`|#` token

ADR-0006 added block-comment nesting as an Options flag, but assumed the `#|` / `|#` delimiter pair was universal. Investigating AutoLISP (derived from XLISP) showed this is false: AutoLISP's block/in-line comment is delimited by `;|` ... `|;` — a different character pair from every other target dialect. We generalize block-comment support to a dialect-supplied `(open, close, nestable)` triple rather than hard-coding `#|`/`|#` with only nesting as a variable. AutoLISP's nesting behavior is unconfirmed in available documentation; we default it to non-nestable pending verification during implementation, consistent with treating undocumented dialect behavior conservatively rather than assuming the more permissive option.
