markers vs. cross-reference insertion

[Robert Lauriston]

I went to insert a cross-reference to a heading and the heading was
not in the picklist for heading 1.

After some investigation I found that there were scores if not
hundreds of index and other markers at the beginning of the target
heading. I deleted them and it showed up in the menu.

Anybody know what markers could cause that? I'd copy the rest of the
markers back from an old copy if I knew what to leave out.