I always add words to my LibreOffice dictionary (standard.dic), but I would love to make those words available to other users by contributing to the project's dictionaries. Is there a way LibreOffice can produce statistics about how often a word is added in dictionaries from users wishing to help? Or is there a project I can join to participate in the dictionaries editing?
Libreoffice is not developed by the Ubuntu development community. This is the place to go if you wish to get involved in the development of Libreoffice:
Also Libreoffice uses Hunspell as the spell-checker. You need to research how Hunspell creates dictionaries.
The user dictionary is just for personal use. LibreOffice does not actually collect words for dictionaries, instead it just assembles existing ones. I think the best way for personal contributions is through Wiktionary from which maybe in the future additional dictionaries can be built.
The best way to add words to a dictionary, is to contact the author of the dictionary.
Check this site to see how: Dictionaries in LibreOffice.