It works fine for me I am also using AEM 6.5 . If you are facing this problem that might because of issue in your template or in your component. Check in We retail project in your local instance. Do you face the similar issue there?Or as Arun suggested use the dedicated buttons to copy and paste.

Experience Fragment can be easily accessed by hitting the URL with "plain" selector for examplehttps://localhost:4502/content/experience-fragment/fragmentName/master.plain.html.see ref https://docs.adobe.com/content/help/en/experience-manager-65/developing/extending-aem/experience-fragments.htmlIf s...

 I think this could be because of the image size, there might be a possibility after uploading the very high resolution image.Update Asset Workflow  takes time to create renditions of that image that is the reason it takes time  to show quick publish button. Try adding smaller resolution image and c...

As Veena mentioned use Custom workflow to change the name of asset. which will change the name of the asset.Just adding on to that ,you can disable the Update Asset workflow for a while while uploading the asset once the asset got uploaded you can enable it. This is for avoiding conflict with Update...

Are you using the OOTB comments componentplease check this https://helpx.adobe.com/in/experience-manager/6-3/communities/using/comments.html If you have your own custom component then in this case you can make a call to your servlet on the click of post button .And servlet can fetch all the previous...

Refer to this below video as well. It has the case study of migration of two projects. What went easy and where they  faced challenges they have explained it all. https://www.youtube.com/watch?v=WomYhJqABks 

After AEM 6.4 there is a change in repository and if you upgrading it to 6.5. I would suggest follow the guidelines provided by Adobe. https://docs.adobe.com/content/help/en/experience-manager-65/deploying/upgrading/upgrade.html 

Accordion component introduced in core components version 2.5.0. Download it from here.https://github.com/adobe/aem-core-wcm-components/releases/tag/core.wcm.components.reactor-2.5.0 

refer thishttps://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/how-to-add-the-author-edit-mode-condition-in-sightly-htl-for/qaq-p/330826 Check for Arun's comment <sly data-sly-test.editor="${wcmmode.edit || wcmmode.design}"></sly><div id="mydivid" class="${editor?'abcd xyz mycla...

If it is not utmost important to use sightly particularly, you can leverage JS(window.location.href ) and jquery to get the URL and then append it html tag where you want it.If you want to use sightly only then I guess you are able to get the full URL except "editor.html".In this case you can form y...