I had implemented a little jquery framework once, to beautify some SharePoint 2013 forms and add some customization (disabling, hiding etc).
To identify the fields and the field type, I use some standard html comments I found in the forms:
<!-- FieldName="URL" FieldInternalName="URL" FieldType="SPFieldURL" -->
Now I work on a (customer) machine where these comments are simply not there (same SP patch level here)... Is there a (site) feature or some setting in Central Administration that could have this site effect?
I tried a couple of different SP farms with different patch levels (including SharePoint Online) and I couldn't reproduce this issue?