this edit broken the page (scroll down at the end to see).
Topic on Talk:Talk pages project/Replying/Flow
There’s an unbalanced <nowiki> in the section titled সাহায্য. This doesn’t cause any issues as long as no </nowiki> appears on the page after it, which is what happened in this edit. While the page appears broken after this edit, it was already broken before, and a non-reply tool edit containing a nowiki’d signature would have also broken it. DiscussionTools tries to avoid “dirty diffs”, i.e. edits that touch other parts of the page, and not breaking the layout would need a dirty diff.
Do you know what the person typed? Tacsipacsi is correct about the source of the problem. Did the person type ~~~~ (unnecessary, but usually harmless)? Or maybe paste the code?
The person (he) was in visual mode. I'm not sure what he typed first. But it looks like at the end he added four tilde, then visual mode automatically added nowiki to escape it. And since there was unbalanced nowiki in the section titled সাহায্য, after saving the reply, it broke the page. I think this is expected behaviour. Only problem was, subsequent edit moved everything in one line, later i fixed that manually.
Well, this second one is certainly a bug. I’ve created a Phabricator ticket for it.