Looks like Facebook is feeling insecure from Twitter. First they introduced mention same as Twitter function and now Timeline, well i don't like Timeline.
Its difficult to mention by using mobile phone. You can mention by using phone if you know the id of the page, person or group. To find out the id of page/group/profile you have to do this simple step.

Finding ID

Group

https://facebook.com/groups/352449594787137
underlined text is group id

Profile

Open any photo from profile and underlined id will be the id of the profile
https://graph.facebook.com/USERNAME
change USERNAME to your Username

Page ID

To find any facebook page id, copy page link and open it by putting graph instead of www
for exapmle
this is page link
https://www.facebook.com/imalon3
open it by changing it as below
https://graph.facebook.com/imalon3
you will page Id there :)

Mention

To mention from a pc, put @ symbol and start typing name of friend to mention.
In mobile, use this to mention any friend.
@[ID:]
change ID to the desired ID, for example @[0945434543427546:] then press share. :)

Get Facebook ID instantly

Type Username or Page Username to get ID