Description:
RFC 4180 describes a CSV file. https://www.rfc-editor.org/rfc/rfc4180
The appropriate appliactoin to open this type of file in libreoffice is calc.
The appropriate application to open a text file is libreoffice writer.
  
When in the writer application opening a .csv file opens the file in writer.
When in the calc app opening a .txt file begins a csv import to calc.

A file with a mimetype text/csv or ending with a .csv extension is a spreadsheet
and should be opened with calc, even if the user is in writer.
A file with a mimetype of text/plain or .txt extension is a text file and should be opened with witer even if the user is in calc.

Or at the very least the filter should give the user the choice of which app  or 'document service' to import with.

Steps to Reproduce:
1.Create a directory in /tmp and with writer create the following
two non native text files with libreoffice in that directory.
Save As 'test.txt'
then save as 'test.docx'
2.Next create two non native spreadsheets in that directory
first fill in some cells and save as 'test.csv' choose csv extension.
Then save as test.xlsx 
3.Next open the csv file with libreoffice calc for editing.
4.use file --> open and open test.docx, ibreoffice will open the file with writer as expected.
5.Go back to the csv file and use File -> open again to open test.txt



Actual Results:
libreoffice will launch a import box thinking this is a spreadsheet.

Expected Results:
Libreoffice should either open the .txt file with writer.


Reproducible: Always


User Profile Reset: Yes

Additional Info:
Same thing happens if you open a .csv file with writer, it opens it as a text document .
I would expect it to launch the import box or just open the file and launch calc
as it does when you open a .xlsx from writer.

I suspect the issue is in filter/source/textfilterdetect/filterdetect.cxx
around line 219