I noticed that whenever Mangahelpers write a new manga shout out, the previous summary for that manga gets replaced. It happened to many series before. One of the latest examples is Hoshi no Ponko to Toufuya Reiko. Yes, my summary is still there for now but it usually gets completely deleted and I won't be suprised when this one meets the same fate.
So my questions are simple. Should I bother adding summaries? Did I miss some rule that says Mangahelpers' summaries take over everything else? Because I don't feel like taking my time to write temporary "placeholders."

I'm pretty sure there's no such rule. Just as you can edit the summary, someone, maybe a mangahelpers user must be doing so too.

Hmm, interesting question... Obviously, it's disrespectful to your work to just replace it with someone else's summary, even though there was nothing wrong with yours. I guess this is a problem with the current MU system, that even though it allows anyone to edit like on wiki, it doesn't have wiki's edit history.

I would say that given the significant risk of your work being wasted by others, it isn't worth your time to provide summaries under the current system. Although personally, I'd never delete someone's summary unless it was thoroughly wrong.

If it makes you feel better, I'm very grateful to you and others who have been writing summaries of manga that isn't being scanlated yet, given that official Japanese summaries are almost entirely useless.

Active translations list
Completed translations list
Dropped translations

Alright. So it's just some user(s?) who likes to promote Mangahelpers. Well, I'm gonna try one more thing. Let's see if he dares to delete really long descriptions. I'm 80% sure Mangahelpers will mention Kenkouki - Hi no Kuni Daiteikokugun Kurenai Ikki Tousentai within a month. It's a new Young Jump series after all.

P.S. Thanks for support cmertb! \o/