When you place (import) a Word document into InDesign, you can choose to use Style Mapping to map the paragraph and character styles in Word to their equivalents in your InDesign document. When you use this feature for the first time in a document, the mappings get stored somewhere and are remembered for any subsequent imports you perform in the same document; you can also choose to save your import settings, including Style Mappings, as a preset to use freely in any document.

If you map any Word styles to the default [Basic Paragraph] style in InDesign, it works as expected the first time (when you actively select [Basic Paragraph] from the dropdown menu). But if you do another import where InDesign reads the Style Mappings from a file – either by using the cached Style Mappings that InDesign has remembered from last time, or by using a saved preset – any style that is mapped to [Basic Paragraph] will not work properly. Instead of mapping the Word style to the existing, built-in [Basic Paragraph], what happens is that a second paragraph style is created with the name [Basic Paragraph], and with properties (font, size, etc.) matching the formatting of the Word style, rather than the built-in [Basic Paragraph] style. This should not even be possible, since you end up with two styles that have the exact same name, but it happens nonetheless (see screenshot).

In order to avoid this, you have to go into Style Mappings and re-select all instances of [Basic Paragraph] manually. Notably, when you open the Style Mappings window, the mappings all look correct, but when you click on [Basic Paragraph], the dropdown menu doesn’t open like it does normally – the text “[Basic Paragraph]” just disappears and the selection field becomes empty. You then have to click a second time for the dropdown menu to open.

This bug has been present for several years (unsure how long). It is present in both Windows and Mac versions of InDesign.

Steps to Reproduce:
1. Create a Word document and type some text in any paragraph style (the default “Normal” will do)
2. Create an InDesign document and place the Word file; make sure “Show Import Options” is selected
3. In the Microsoft Word Import Options window, select “Customise Style Import” and click on “Style Mapping”, then map the style used in the Word document to [Basic Paragraph]; click OK twice and click somewhere in the document to import the text
4. Place the Word file again in the same way, using the cached Style Mappings which InDesign automatically remembers without changing anything (you can even deselect “Show Import Options” and skip that part entirely)

Actual Result:
After the second import, your document has two paragraph styles, both named “[Basic Paragraph]”, see screenshot. One is the built-in default style; the other is an erroneously created doublet and has the little ‘arrow-into-a-box’ icon to show that it is an imported/auto-created style. The text imported the first time is styled with the built-in [Basic Paragraph] style; the text imported the second time is styled with the imported ‘parasitic’ [Basic Paragraph] style.

Expected Result:
After the second import, there is only one paragraph style in the document, the built-in [Basic Paragraph] style. All the text in the document, both that imported in the first import and that imported in the second import, is styled with this built-in [Basic Paragraph].

Any Workarounds:
Every time you place a Word file, always enter the Style Mapping window and manually reselect [Basic Paragraph] from the dropdown menu for all styles that map to this style. Alternatively, after importing the file, delete the ‘fake’ [Basic Paragraph] style and when asked what to do with the text, select the real [Basic Paragraph] style to replace it.