Without WailaHarvestability broadswords can destroy cowebs very fast. But when this mod is installed it marks broadsword as not effective and it takes lots of time to destroy single coweb.

Take look at screenshots here:
SlimeKnights/TinkersConstruct#2518

Using lastest version of TiC, Waila/Harvestability and forge.

Yeah that is indeed the case, very weird. I will look into this later :)

@squeek502 I have tracked it down to https://github.com/squeek502/WailaHarvestability/blob/1.7.10/java/squeek/wailaharvestability/setup/MissingHarvestInfo.java#L14. If you remove that code it works just like it should for both vanilla and Tinkers Construct swords. I'm not quite sure why you have done it like that though :)

Blocks.web.setHarvestLevel("sword", 0) is done so that "Sword" shows up as the effective tool. Without that, nothing shows up at all (sword effectiveness is hardcoded in the web block code in a non-standard way IIRC). Would need to look at why the TiC tools are affected by this, though--maybe they set some other harvest level?

@Tomash667 which version of Minecraft are you using?

I assumed he was using latest 1.10.2 versions, which was the versions I was able to reproduce this with.

Ahh yeah you are right. Removing the code just fixes that the cob web aren't harvestable by TiCon swords, but it also removes the "Effective Tool" part.
I'm pretty sure the problem is that TiCon swords are not a sword in the vanilla/forge sense. As you can see in Tomash667s screenshots in the issue on TiCons issue tracker, Waila Harvestability does not think it is a sword.

Tinkers Construct does their cob web effectiveness code here: https://github.com/SlimeKnights/TinkersConstruct/blob/25a03943276b131e4dcbc74907c887491de343a8/src/main/java/slimeknights/tconstruct/library/tools/SwordCore.java

Yeah, might be worth getting TiC to add setHarvestLevel("sword", 0); to SwordCore?

Also, just to make sure, this is a visual bug only, right? Waila Harvestability should only affect the client side so TiC swords should still be effective even if they don't visually appear to be.

No it is not a visual bug only. It actually makes you unable to break cob web with TiCon swords (Even though Waila Harvestability is client-side only, which is weird o.O)

@squeek502 It is as @GirafiStudios written. It's marked as not effective and can't break coweb.

Minecraft/forge version: 1.10.2-forge1.10.2-12.18.2.2111
TConstruct-1.10.2-2.5.6b
Mantle-1.10.2-1.1.1
Waila-1.7.0-B3_1.9.4
WailaHarvestability-mc1.10.2-1.1.9

@bonii-xx agreed, thanks for adding support on your end though.

I added the sword compatibility, but you probably still should fix it on your side, since you're still changing the properties of vanilla cobwebs.