Bug shipped in v0.4.5. The leading <%# %> comment in
studio/modals/_host.html.erb contained a worked example of the
consumer's render-block syntax using <%%= ... %%> escapes. ERB scans
for the first %> sequence to close the comment, and %%> ends in %>,
so the comment terminated mid-escape — leaving the example markup
AND the prose after it as literal text at the bottom of every page
that rendered the host (visible on /contests, /, anywhere the modal
stack was empty).

Fix: remove embedded ERB escapes from the comment. Worked example
lives in README / CHANGELOG instead. No API change; no consumer
code changes needed beyond bundle update.