Condemn uses, not chart types

The pie page argued the form was the problem ("asks the reader to
compare angles") and then conceded a narrow exception; the dual-axis
page named the form in its title and rated it severity 5. Both read as
blanket bans, which is not the position — and blanket bans are how
dataviz advice turns into the folklore we're trying to replace with
citations.

The pie page now says outright that the chart type isn't the sin, the
workload is, and keeps the pie for the job it does well. The dual-axis
page is retitled for the actual misuse, drops to severity 4, and gains
a section on when a second axis is legitimate — the test being whether
you chose the alignment yourself.

Adds a severity rubric to CLAUDE.md so this stays consistent: 5 is
reserved for charts with no honest reading, and a form with legitimate
uses caps at 4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ULE5RRxdQE1ebwefEd2eCM

docs/content-backlog.md

@@ -27,28 +27,28 @@ seven sources, give it seven and add whatever's missing to the file.
 
 | Reference | Cited by |
 | --- | --- |
-| `munzner` | — |
-| `healy` | — |
-| `schwabish` | — |
 | `ftvisvocab` | — |
-| `tufte` | truncated-y-axis |
-| `huff` | truncated-y-axis |
-| `swd` | two-y-axes |
-| `spurious` | two-y-axes |
-| `datawrapper` | two-y-axes |
+| `healy` | — |
+| `munzner` | — |
+| `schwabish` | — |
+| `datawrapper` | dual-axis-correlation |
 | `fewpies` | too-many-pie-slices |
-| `showmenumbers` | too-many-pie-slices |
+| `huff` | truncated-y-axis |
 | `shapeparameter` | aspect-ratio |
+| `showmenumbers` | too-many-pie-slices |
+| `spurious` | dual-axis-correlation |
+| `swd` | dual-axis-correlation |
+| `tufte` | truncated-y-axis |
 | `vizwtf` | inverted-y-axis |
-| `wilke` | too-many-pie-slices, truncated-y-axis |
-| `truthfulart` | aspect-ratio, two-y-axes |
 | `callingbullshit` | inverted-y-axis, truncated-y-axis |
-| `economistmistakes` | inverted-y-axis, truncated-y-axis |
-| `datatoviz` | too-many-pie-slices, two-y-axes |
-| `junkcharts` | inverted-y-axis, too-many-pie-slices |
+| `datatoviz` | dual-axis-correlation, too-many-pie-slices |
 | `eagereyes` | aspect-ratio, too-many-pie-slices |
+| `economistmistakes` | inverted-y-axis, truncated-y-axis |
+| `junkcharts` | inverted-y-axis, too-many-pie-slices |
+| `truthfulart` | aspect-ratio, dual-axis-correlation |
+| `wilke` | too-many-pie-slices, truncated-y-axis |
 | `clevelandmcgill` | aspect-ratio, too-many-pie-slices, truncated-y-axis |
-| `howchartslie` | aspect-ratio, inverted-y-axis, truncated-y-axis, two-y-axes |
+| `howchartslie` | aspect-ratio, dual-axis-correlation, inverted-y-axis, truncated-y-axis |
 
 The citation lists in each entry below are **starting points, not budgets** —
 add to them while drafting.
@@ -198,6 +198,13 @@ rediscovering them:
 
 ## Conventions reminder
 
+Note what the two pie entries above do and don't say. Neither condemns the pie
+chart — both condemn feeding one data that has no whole to divide. Same for a
+second y-axis: the form is fine, the manufactured correlation is not. We don't
+ban chart types here, and a backlog entry that reads like a blanket ban has been
+written wrong. See the severity rubric in `CLAUDE.md` — a form with legitimate
+uses caps out at 4.
+
 Anything picked up from this list still follows `CLAUDE.md`: the title names the
 problem plainly and leaves the wit to the poke, the poke names the general sin
 and never our sample's numbers, both charts share one dataset, and the fixed