I'm not sure to understand the exact feature exposed here.

Is the final goal to have a "Join the supporters" button on the bottom of https://meta.wikimedia.org/wiki/Wiki_Loves_Love#Support so people just have to click, and will be prompted with some "tank you" message?

@Psychoslave, not exactly. The final goal is:

• One message to "thank you" to the supporters in theirs talk pages.
• Another message to leave in the village pumps to encourage another users to join the initiative.

Ok. So far I thanked people who signed the support section on Meta through the Mediawiki "thank" feature.

For the first point, I would have spontaneously thought more of something like a bot, but since you talked about template, I guess that it's not what you had in mind. So it might involve something like a javascript modifying several page at the same time. I didn't made such a thing so far on Mediawiki. I plan to learn that in the coming time, especially OOUI, but if anyone is already skilled on this tools, please go on, just let me know if you need review. :)

The second point is purely about writing some promotional, isn't it?

In T193796#4181237, @Psychoslave wrote:

Ok. So far I thanked people who signed the support section on Meta through the Mediawiki "thank" feature.

For the first point, I would have spontaneously thought more of something like a bot, but since you talked about template, I guess that it's not what you had in mind. So it might involve something like a javascript modifying several page at the same time. I didn't made such a thing so far on Mediawiki. I plan to learn that in the coming time, especially OOUI, but if anyone is already skilled on this tools, please go on, just let me know if you need review. :)

Well, having a bot for this task could be a good idea. I thought about it, but at this moment there isn't many activity. But if you consider that it could be better, with perspective of future, we can work in it. When I said a template, I mean to create a template with the message, to extract automatically the username (for example) when someone of us post a new message in the talk page of the supporters. Of course, the bot would light this task. But I never operated a bot in Commons, so I don't know how hard is the procedure or if we can use one you have.

If we have to create a new bot, maybe we can open a task about it; please, if you consider it would be better, create the task and propose it. We could run the bot in PAWS. May be @Chicocvenancio could have more ideas about it.

In T193796#4181241, @Psychoslave wrote:

The second point is purely about writing some promotional, isn't it?

Yes, a promotional text, an announcement like:

Wiki Loves Love is a proposal for a new contest... We encourage to you to check the page and give ideas... If you find it interesting, you can support the project!

Something similar obviously, I have only exposed some sentences to understand what we are looking for.

I started something on the second point, see https://commons.wikimedia.org/wiki/Commons:Wiki_Loves_Love/Appreciation

I think that before we launch that, it would be better to have a simple "support" blue button, that directly edit the page, without requiring to type any wikitext.

In T193796#4184485, @Psychoslave wrote:

I think that before we launch that, it would be better to have a simple "support" blue button, that directly edit the page, without requiring to type any wikitext.

@Psychoslave, something like this or like this?

In T193796#4184480, @Psychoslave wrote:

I started something on the second point, see https://commons.wikimedia.org/wiki/Commons:Wiki_Loves_Love/Appreciation

I have read as I can at this hours with the tiredness I have, but it sounds fine! But it seems more for the second message, the announcement and not for the appreciation who support the project:

In T193796#4180528, @Ivanhercaz wrote:

• One message to "thank you" to the supporters in theirs talk pages.
• Another message to leave in the village pumps to encourage another users to join the initiative.

First, the appreciation, and the second the announcement, so the title of the subpage should be change to "Announcement" or "Announcement 2018".

Okay, I have read now T193952. Tomorrow I will check it fine.