I think people generally prefer undo support (it would make sense to do it for all of desktop/mobile, Flow/non-Flow, we have it for none currently).

See T71636: Thanks: Implement an undo feature and linked tasks.

+1. Just noticed this on mediawiki.org. There's a Thank button for every post at https://www.mediawiki.org/wiki/Topic:Sgfi0l5w96dhfmqb and clicking it immediately performs the action.

There is no confirmation step, no undo option, and also it doesn't seem very clear what happened or where it goes. The only thing that changes is it changing to "Thanked" and no longer being clickable. Although the clickable and unclickable variant are styled and positioned the same, yet behave different (UX inconsistency).

Also, on refresh it is gone. So I can apparently click it again the next time. This is inconsistent with e.g. action=history of a regular wiki page where the change to "Thanked" is permanent and survives a refresh.

In T101196#1480951, @Krinkle wrote:

The only thing that changes is it changing to "Thanked" and no longer being clickable. Although the clickable and unclickable variant are styled and positioned the same, yet behave different (UX inconsistency).

In Vector:

• Before clicking, it has a pointer/hand indication, turns green on hover, and is #666 when not hovered.
• After clicking, it has no pointer/hand indication (instead the standard text caret when hovered), does not change color on hover, and is #898989 when not hovered.

Granted, the differences between the two not-hovered gray is very subtle. But the more important differences are:

• The word. This alone is the main explanation.
• The on-hover behavior.

However, there may be ways to make it more obvious. What do you have in mind?

Also, on refresh it is gone. So I can apparently click it again the next time.

It won't actually send thanks a second time. Nevertheless, this is a bug: T101342: Don't make it seem user can re-thank for a Flow post when they already did; render server-side