Thank you so much for your very quick response to my question and I do appreciate your hard work!
My specific question here is about the middle name and preferred name data.
I exported a GEDCOM from WikiTree earlier today and imported it to GRAMPS 3.4.2-1 and Family Tree Builder 6.0.0. In both cases all middle name and preferred name data was missing. For example [[Wilson-11117|Clifford Augustus (Gus) Wilson]] was loaded into both programs as simply "Clifford Wilson". The middle name, Augustus, and preferred name, Gus, were both lost.
Whilst Family Tree Builder totally lost the data, GRAMPS stored the following in a person note:
Records not imported into INDI (individual) Gramps ID I0091:
Line ignored as not understood Line 7130: 2 _PGVN Gus
Line ignored as not understood Line 7131: 2 _MIDN Augustus
I have looked up PGVN and MIDN in the GEDCOM 5.5 standard at http://homepages.rootsweb.ancestry.com/~pmcbride/gedcom/55gctoc.htm and at http://en.wikipedia.org/wiki/GEDCOM#GEDCOM_model and can find no reference to either tag.
As I am not an expert, I may be missing something (apologies if so) but it appears the data cannot be loaded because of non-standard tags.
This is separate to any issue about what is stored in the text area on WikiTree as these data are held in unique fields.
I hope this is helpful. Do let me know if you need any more information.