Member can't post comment on article.
I asked IPS support about it and they told me :
This issue is caused by your application "Keyword Tooltips". Essentially what was happening was people would attempt to comment on the article, but the application was causing that to error out. Thus the system was showing who the last commenter was but the comment wasn't being saved. I've disabled the application and everything is working correctly now.
Please contact the author of the application about the issue and a fix for it.
If you want more details, please contact me