@kudra This is a Friendica support question 😁
@noam Perhaps you can use the content filter to filter out hashtags (they will be colapsed afaik). Go to Settings > Addons > Content filter (NSFW and more) and add the terms.
It says there Use /expression/ to provide regular expressions, #tag to specfically match hashtags (case-insensitive), or regular words (case-sensitive) - so I guess it should do the trick (I haven't tested against hashtags myself so far).