Hi
I’m very sorry, but this is not really caused by the plugin. The plugin is not creating any files on the disk, at least not by design.
Actually, the issue is related to the setup of your webhosting provider. They use NFS (= network file system) and this can create such files on the disk under special circumstances — when app creates a file, then removes it, but the file can be still accessed. In those cases remnant files .nfs*** can be found on a disk.
I guess, that this might be related to embedding of links to the chat messages. But it is only a guess. I can imagine, that when the plugin accesses the remote link to embed the content to the message, PHP can (on the background) store the content of the remote webpage temporarily on the disk, in the end leading to a problem explained in the previous paragraph.
If my guess is right, then you can try to switch off “By enabling this submitted URLs will become clickable.” in widget options. This will disable all embeds and if the guess is right, then it will also stop the creation of the .nfs*** files.
I plan for the future to have a separate option for embeding — so you can still have links clickable, but content not embedded to the messages. I will make sure this comes in near future.
Another possibility would be to make a cron job that would regularily delete .nfs**** files from the folder.
Also, the issue with .nfs*** files should be solved by using NFS v4.1 with OPEN4_RESULT_PRESERVE_UNLINKED (see here), but I’m not sure if your webhosting provider would be willing to this solution.
Last possibility is to change a webhosting provider for one that is not using NFS. If they stored the files just locally on the server, then NFS would be out of game.
/Honza
