[[ https://www.mediawiki.org/w/index.php?title=Topic:Tk5fyk5lkovwtclc&topic_showPostId=tk82le8uyk9lrgns#flow-post-tk82le8uyk9lrgns | Pearli at mw.org:
lets suppose you want to edit the site https://en.wikipedia.org/wiki/Overwatch_(video_game)?veaction=editsource on english wikipedia. If u try to mark a big text passage like the first two sections **from bottom up to top**, the browser always jumps to the cursor position where you started. It is not importand which text passages you want to mark. It happens to all, with and without wiki-syntax.
The 2nd thing, **top to down**, is a bit harder, it didn't jump to the bottom of the page, it is hopping large, large text passages down. You can't really do accuracy work if this happens. It is a bit frustrating and i switched to old wikitext editor to "solve" the problem and switched back after i finished my work.