Problem: you need to attribute content in a page to multiple authors after refactoring.
The signed work of others, even if very brief in word-count, may have had substantive influence on the content development as a whole. Other changes, more cosmetic or editorial in nature, may seem larger.
Respect signatures on large-scale contributions: Don't delete signatures from opinion pieces or original work and don't change the meaning of a signed work.
Create attribution groups: One possibility is having three classes of page authorship: lead/core author(s), editor(s), and other contributor(s). The first create most of the content, the second tidy/refactor/polish content, and the third do little bits here and there, ask questions, etc. For authors who contribute pretty much everywhere in a page, give their names, in the appropriate groups, at either the top or bottom (or both!) of the page.
Collect attributions of page segments: If an author only ever contributed to one section of a page, consider adding an appropriate attribution for the author only to the section, say
“Some content in this section by NAME HERE.”