Log off, restart device and log in.
This may be a forum software to certain devices problem or on your end.
In the past, when I've logged on via a desktop and later use my cell, the forum 'expects' me to be on a computer and the page is formatted larger then my cell's viewable window w no way to resize from my cell. Have to go to a computer and hit crtl - to reduce the screen size, then back to my cell and pages are formatted for my cell again.
Not the same problem you're having but similar.
Chrome and Firefox have both done updates recently that also cause problems w the forum loading correctly. Esp those running certain anti-virus and ad blocker software. But not for everyone whoch makes it even odd'r.
EDIT: Loaded and posted from my cell correctly
EDIT1: Edit did too