This seems to be a similar issue to that experienced by Greg @gkittinger
Thanks for letting me know, as this means that we're at least having a pattern. Also, the problem seems to occur with comments, but not articles or forum posts/replies. At this point I strongly suspect that the trouble has to do with our recent core upgrade, where some elements of the comment form have been changed.

The bad thing is that we're still unable to replicate this on our end and judging from the activity log at the site, other users are able to leave comments. This makes searching that bit more difficult, so please bear with us as this might require multiple tests

I have now disabled the CDN caching to ensure that anything your browser reads is being pulled directly from the site. Any improvement?

I still cannot post a thing! Just tried again to comment on Stellan's wood grain article - no result!

This is the text i get when trying to add more photos.

Error: File is too big. The maximum allowed file size is 8.0 MB. Australien 2015 1341.JPG

Do I have to resize them and save again or is there an actual problem...thinking if photos are bigger files as I used different camera for these photos...I can try add another article with photos from other camera.

@stellan Re: Error: File is too big. The maximum allowed file size is 8.0 MB. Australien 2015 1341.JPG

The system must have a restriction on maximum file size to prevent potential abuse of server resources. Actually, we have once increased this limit from 6 to 8MB to accommodate new camera models. Are these files really over 8MB each? The way to check (Windows): right-clik on the file name, then select "properties" from the menu, then look for what the "size" says.

I'd be grateful for this check, and also for info on the camera model.

Thank you

@gkittinger and @robertandy. Thank you for bearing with me on this, now is the time to ask for another test.

We have discovered that there was a high load on our database server, which BTW has been causing some trouble w/accessing the site this morning. Really, there's no way of knowing if your problems have been related to the database, but as we have now done a complete reset of it, I would like to ask you for another quick comment posting test.

Your patience is greatly appreciated.
Kind regards,
/m

But oddly enough I could reply here?

I tried as well - and no success. Still cannot comment.