I think what you're describing the phenomenon of Paragraph Composer versus Single Line composer.
(more here Text composition)
InDesign is automatically set to Paragraph Composer.
Here's the differences:
Adobe Paragraph Composer
InDesign’s Adobe Paragraph Composer (called the Multi-Line Composer in previous versions) is selected by default. It takes a broader approach to composition by looking at the entire paragraph at once. If a poorly spaced line can be fixed by adjusting the spacing of a previous line, the Paragraph Composer reflows the previous line. The Paragraph Composer is governed by the following principles:
The evenness of letter spacing and word spacing is the highest priority. The desirability of possible breakpoints is determined by how much they cause word and letter spacing to vary from the Desired settings.
- Uneven spacing is preferred to hyphenation. A breakpoint that does not require hyphenation is preferred over one that does.
- All possible breakpoints are ranked, and good breakpoints are preferred over bad ones.
The paragraph composer is more sophisticated than the single-line option, offering generally better overall spacing because it sacrifices optimal spacing a bit on one line to prevent really bad spacing on another, something the single-line method does not do.
However, there is one frustration in dealing with the paragraph composer: When you try to edit text or play with tracking to get rid of an orphan or widow, the paragraph composer keeps adjusting the text across several lines, often counteracting your nips and tucks. The single-line composer doesn’'t do that.
Adobe Single-Line Composer.
In the past, programs like QuarkXPress and PageMaker have used single-line composition methods to flow text. This method marched line by line through a paragraph and sets each line as well as possible using the applied hyphenation and justification settings. The effect of modifying the spacing of one line on the lines above and below is not considered in single-line composition. If adjusting the space within a line causes poor spacing on the next line, tough luck. When you use Adobe Single-Line Composer, the following rules apply:
- Adjusting word spacing is preferred over hyphenation.
- Hyphenation is preferred over glyph spacing.
- If spacing must be adjusted, removing space is preferred over adding space.
This is exactly what was happening. I'm gonna go ahead and use single-line composer.
Thank you very much!