Questions of the legality of various sprint mods were first brought up when iusethisforgood was banned for using an absolute sprint mod:

http://www.reddit.com/r/Civcraft/comments/18lm9e/official_evidence_and_accusations_against/

u/kk- then did a good job of laying out many of the issues and the types of sprint mods that people use:

http://www.reddit.com/r/Civcraft/comments/18lm9e/official_evidence_and_accusations_against/c8g7swn

this bit in particular is useful:

Sprint Modifications

Sprint modifications are quite popular, and as highlighted in the OP, operate on multiple different general methods:

1.)A macro that quickly simulates a double press of the forward key.

2.)A modification that uses a binding to replicate the behaviour of the second forward key press when a user wants to sprint (Almost functionally equivalent to 1, but not necessarily subject to the glitches associated with

3.)A modification that 'absolutely' toggles sprinting, and when toggled will always cause the player to sprint; they can even stand still and they will still appear to be sprinting and have all the benefits of sprinting.

Then in the ruling on iusethisforgoods case there is a lot more information on this from the administrative side:

http://www.reddit.com/r/Civcraft/comments/18ue9d/civcraft_v_iusethisforgood/

A specific statement here by CJD informs the community that using a key map to replace the functionality of sprint without using an absolute sprint is legal. This seems to allow both 1. and 2. in kk- description by holy edict of CJD himself.

Now, what is confusing to me is the following exchange:

http://www.reddit.com/r/Civcraft/comments/1tbrib/gg/ce6klnn

KingXvs describes using exactly the nonabsolute sprint keybinding method that kk- layed out and CJD allowed. Strangely today, ttk2 says it is cheating. ttk2 has said that they checked very carefully and it "looks identical to cheating" but of course claiming that something is cheating because it looks identical and fits the definition is completely circular. I think laying out the variety of sprint mods, classifying them, and disallowing some according to the rules and precedents is a better was to proceed than banning players here and there saying "you were cheating from the servers perspective".

I am also quite certain that Positronic (/u/adhavoc ) used control pack as the dominant PvPer near the end of 1.0 in exactly the same way as KingXvs. I know this because Positronic taught me to use Control Pack in this exact fashion on CivPvP. I am also certain that Positronic was not the only one to do this without issue for months.

A discussion from the community and administration on these matters would be appreciated. There was uncertainty in the PvP community about which sprint mods were allowed for months, and months ago an answer was squeezed out of CJD. Since then it is undeniable that the control pack sprint method along with similar methods have been in wide use in the CivCraft PvP community.

Edit:

In a new statement ttk2 has said that control pack is allowed, as long as there is "enough delay"

http://www.reddit.com/r/Civcraft/comments/1tbrib/gg/ce6onln

What this comes down to is likely ttk2's understanding of the limits of human timing. Essentially he believes that sprinting was restarted too quickly after being cancelled. You can see ttk2s view on human timing limits here:

http://www.reddit.com/r/Civcraft/comments/1j9lf9/i_am_bloodidiot_ama/cbciwxj#cbciwxj

Where he claims that human actions in sequence can be no faster than 50ms. So the moral of the story is , don't be fast at clicking and stuff. Don't train hard and get better timing than other players using the same mods because nocheat will flag you a lot and then you will be cheating by definition.

Really though, even with a vanilla client it would be possible to use a keyboard with mechanical properties that are favorable to double tapping 'w' very fast so that the timing would be indistinguishable from the fastest someone could hit a bound sprint key while holding 'w'. You could even bind w keydown to one tap, and w keyup to another, you could do this with software or do something very similar with a mechanical apparatus. The ultimate timing limits for double tapping 'w' vs holding 'w' and pushing another key are the same, unless you are going to disallow mechanical keyboard mods or rebinding key up/down events at an OS level with a vanilla client.

Also it should be clear to everyone that while there are human reaction time limits, there is essentially no lower timing limit to events in a planned sequence. If a player has their sprint cancelled and recovers it in say 20ms, this is not actually an indication that they are cheating because they can see that someone is running at them and plan to resprint in advance, so there is actually no reaction time limit, as they could even resprint before they were hit, and thereby have apparently negative reaction time.