Deleting markup can kill the script that survives it

Removing a UI block also removes the ids the page script binds to, and document.getElementById(x).addEventListener on a now-null node throws a TypeError that aborts the rest of the script file. Anything wired later in the same IIFE — a scroll-triggered reveal, a clipboard handler, an observer — silently never initialises, and the page looks merely unfinished rather than broken. Before deleting markup, grep the script for every id and class inside the block being removed, then assert console error count is zero and re-test the unrelated features that come after it in source order. This is the same failure family as an IntersectionObserver pointed at a display:none or display:contents node: no exception surfaces to the user, so only a console-error assertion catches it.