The reading problem
Keep word gaps from becoming the main visual rhythm.
A concrete example
A narrow community notice set flush on both edges may stretch spaces between words unevenly. A left-aligned version is easier to scan and makes line endings natural.
Try this edit
Switch the paragraph to left alignment and compare at phone width. Look for unusual gaps, broken words, and a final line that feels detached. Keep the setting that makes the message easier to follow.
Proof on the page
Set the same narrow notice once with full justification and once with left alignment. Keep the font, width, and words fixed. Notice whether stretched spaces form vertical rivers in the justified copy. At mobile width, verify the aligned-left version still reflows rather than pushing a long word off screen. This is a direct comparison of the setting, not a rewrite of the content.
Where the method stops
A paragraph can be left aligned and still be hard to read because of dense language, low contrast, or a cramped container. Do not infer a pass from one setting. When language direction differs from English, alignment choices need a fresh check with the actual text and readers; this guide does not generalize one layout to all scripts.