There are at least half a dozen new requests for this feature. IT is really necessary to be able to:
1. estimate how much time it will take
2. log how much time you spent on this (anybody can log time, not only the assignee)
3. comment when you log time, to explain why you logged -> this should come as a different style comment
4. in a future expansion, be able to extrapulate data regarding time estimates and time spent.

as for the percentage, it can simply be how much time you spent on how much you estimate -> I don't personally see value in this metric.

this is really a part of this: https://freedcamp.uservoice.com/forums/126945-suggestions-for-features/suggestions/2082345-integrate-tasks-and-time-applications-in-freedcamp isn't it?

There are strong similarities with this one: https://freedcamp.uservoice.com/forums/126945-suggestions-for-features/suggestions/15707391-time-tracking-entries

Please let this be on an opt-in basis: admin should be able to decide wether this is active. Imagine a large team with not-so-good training on methodology. Image the rule *should* be to have only one responsible for task (collaborators are to be in subtasks). The team is not well trained and, instead of tasks, more than one user auto-assigns the issue to themselves. This is not good, and puts overhead on the team leader that has to sort that out. It would be good to have it disabled per default and opt-in (or opt-out, the same goes the other way around).